Matriptase, a serine protease and its applications

ABSTRACT

The invention is directed to a method of detecting a malignancy or a pre-malignant lesion in breast or other tissue, or a pathologic condition, by detecting the presence of single-chain or two-chain forms of matriptase in the tissue. The invention is further directed to a method of treating malignancies, which have the phenotype of matriptase production by administering a tumor formation inhibiting effective amount of concentrate of Bowman-Birk inhibitor (BBIC), or other matriptase inhibitor. The invention also is directed to nucleic acids encoding a matriptase protein or fragments thereof, and their use for structure elucidation and modeling to identify other inhibitors of matriptase, as well as to methods of identifying matriptase modulating agents, including activators and inhibitors.

GOVERNMENT RIGHTS

This invention was developed under federally sponsored research projects (e.g. NIH grant Nos. 1R21CA80897, 2P50CA58158 and DOD Grant BC980531), therefore the United States Government may have certain rights in the invention.

FIELD OF THE INVENTION

This invention relates to the field of proteases found in human breast milk and other normal tissue, and to the differentiation of complexation patterns between the proteases and their cognate inhibitors found in normal breast milk, in normal tissues, and incancerous and pre-cancerous tissue of the breast, as well as from other body tissues obtained on biopsy, and in other body fluids such as from nipple aspirate.

BACKGROUND OF THE INVENTION

Serine Proteases and Other Cancer Related Proteases. Elevated proteolytic activity has been implicated in neoplastic progression. While the exact role(s) of proteolytic enzymes in the progression of tumor remains unclear, it seems that proteases may be involved in almost every step of the development and spread of cancer. A widely proposed view is that proteases contribute to the degradation of extracellular matrix (ECM) and to tissue remodeling, and are necessary for cancer invasion and metastasis. A wide array of ECM-degrading proteases has been discovered, the expression of some of which correlates with tumor progression. These include matrix metalloproteases (MMPS) family, plasmin/urokinase type plasminogen activator system and lysosomal proteases cathepsins D and B reviewed by Mignatti et al., Physiol. Rev. 73: 161-95 (1993). The plasmin/urokinase type plasminogen activator system is composed of plasmin, the major ECM-degrading protease; the plasminogen activator, uPA; the plasmin inhibitor α2-anti-plasmin, the plasminogen activator inhibitors PAI-1 and PAI-2; and the cell membrane receptor for uPA (uPAR) (Andreasen et al., Int. J. Cancer 72: 1-22 (1997)). The MMPs are a family of zinc-dependent enzymes with characteristic structures and catalytic properties. The plasmin/urokinase type plasminogen activator system and the 72-kDa gelatinase (MMP-2)/membrane-type MMP system have been received the most attention for their potential roles in the process of invasion of breast cancer and other carcinomas. However, both systems appear to require indirect mechanisms to recruit and activate the major ECM-degrading proteases on the surface of cancer cells. For example, uPA is produced in vivo (Nielson et al., Lab. Invest. 74: 168-77 (1996); Pyke et al., Cancer Res. 53: 1911-15 (1993); Polette et al., Virchows Arch. 424: 641-45 (1994); and Okada et al., Proc. Natl. Acad. Sci. USA 92: 2730-34 (1995)) in human breast carcinomas by myofibroblasts adjacent to cancer cells and must diffuse to the cancer cells for receptor-mediated activation and presentation on the surfaces of cancer cells. However, the uPA receptor (uPAR) is detected in macrophages that infiltrate tumor foci in ductal breast cancer. Somewhat analogously, the majority of the MMP family members, such as 72-kDa/Gelatinase A (MMP-2) (Lin et al., J. Biol. Chem. 272: 9147-52 (1997)), stromelysin-3 (MMP-11) (Matsudaira, J. Biol. Chem. 262: 10035-38 (1987)), MTMMP (MMP-14), are expressed by fibroblastic cells of tumor stroma, or surrounding noncancerous tissues, or both. Indirect mechanisms of activation and recruitment of Gelatinase A in the close vicinity of the surfaces of cancer cells have been proposed, such that an unidentified cancer cell-derived membrane receptor(s) of Gelatinase A could serve as membrane anchor for Gelatinase A; cleaved MT-MMP from stroma cells could then diffuse to the surfaces of cancer cells to activate Gelatinase A. Matrilysin (MMP-7; Pump-1) appears to be the only MMP which is found predominantly in the epithelial cells.

The stromal origins of these well-characterized extracellular matrix-degrading proteases may suggest that cancer invasion is an event which either depends entirely upon stromal-epithelial cooperation or which is controlled by some other unknown epithelial-derived proteases. Search for these epithelial-derived proteolytic systems that may interact with plasmin/urokinase type plasminogen activator system and/or with MMP family could provide a missing link in our understanding of malignant invasion.

Matriptase was initially identified from T-47D human breast cancer cells as a major gelatinase with a migration rate between those of Gelatinase A (72-kDa, MMP-2) and Gelatinase B (92-kDa, MMP-9). It has been proposed to play a role in the metastatic invasiveness of breast cancer. (See U.S. Pat. No. 5,482,848, which is incorporated herein by reference in its entirety.) The primary cleavage specificity of matriptase was identified to be arginine and lysine residues, similar to the majority of serine proteases, including trypsin and plasmin. In addition, matriptase, like trypsin, exhibits broad spectrum cleavage activity, and such activity is likely to contribute to its gelatinolytic activity. The trypsin-like activity of matriptase distinguishes it from Gelatinases A and B, which may cleave gelatin at glycine residues, the most abundant (almost one third) of amino acid residues in gelatin.

Kunitz-type serine protease inhibitors. Hepatocyte growth factor (HGF) activator inhibitor-1 (HAI-1) is a Kunitz-type serine protease inhibitor which is able to inhibit HGF activator, a blood coagulation factor XII-like serine protease. The mature form of this protease inhibitor has 478 amino acid residues, with a calculated molecular mass of 53,319. A putative transmembrane domain is located at its carboxyl terminus. HAI-1 contains two Kunitz domains (domain I spans residues 246-306; domain II spans residues 371 to 431) separated by a LDL receptor domain (residues 315 to 360). The presumed P1 residue of active-site cleft is likely to be arginine-260 in Kunitz domain I and lysine 385 in domain II by alignment with bovine pancreatic trypsin inhibitor (BPTI, aprotinin) and with other Kunitz-type inhibitors. Thus, HAI-1 has specificity against trypsin-type proteases. Although HGF activator is exclusively expressed by liver cells, HAI-1 was originally purified from the conditioned media of carcinoma cells as a 40-kDa fragment doublet, rather than the proposed, mature, membrane-bound, 53-kDa form (Shimomura et al., J. Biol. Chem. 272: 6370-76 (1997)).

The protein inhibitors of serine proteases can be classified into at least 10 families, according to various schemes. Among them, serpins, such as maspin (Sheng et al., Proc. Natl. Acad. Sci. USA 93: 11669-74 (1996)) and Kunitz-type inhibitors, such as urinary trypsin inhibitor (Kobayashi et al., Cancer Res. 54: 844-49 (1994)) have been previously implicated in suppression of cancer invasion. The Kunitz-type inhibitors form very tight, but reversible complexes with their target serine proteases. The reactive sites of these inhibitors are rigid and can simulate optimal protease substrates. The interaction between a serine protease and a Kunitz-type inhibitor depends on complementary, large surface areas of contact between the protease and inhibitor. The inhibitory activity of the recovered Kunitz-type inhibitor from protease complexes can always be reconstituted. The Kunitz-type inhibitors may be cleaved by cognate proteases, but such cleavage is not essential for their inhibitory activity. In contrast, serpin-type inhibitors also form tight, stable complexes with proteases; in most of cases these complexes are even more stable than those containing Kunitz-type inhibitors. Cleavage of serpins by proteases is necessary for their inhibition, and serpins are always recovered in a cleaved, inactive form from protease reactions. Thus, serpins are considered to be suicide substrate inhibitors, and their inhibitory activity will be lost after encounters with proteases. The suicide nature of serpin inhibitors may result in regulation of proteolytic activity in vivo by direct removal of unwanted proteases via other membrane-bound endocytic receptors (in the case of uPA inhibitors). However, the Kunitz type inhibitors may simply compete with physiological substrates (such as ECM components), and in turn, reduce their availability for proteolysis. These differences may result in different mechanisms whereby these proteases perform their roles in ECM-degradation and cancer invasion.

It has previously been disclosed that a soybean-derived compound known as Bowman-Birk inhibitor (BBI, from Sigma) may have anti-cancer activity by preventing tumor initiation and progression in model systems.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1: Identification and partial purification from human milk of 110- and 95-kDa proteins immunoreactive to anti-matriptase mAb 21-9. Human milk proteins were fractionated into two pools by addition of ammonium sulfate: a 0-40% pool (A) and a 40-60% pool (B). Both fractions were further purified by DEAE chromatography. The DEAE fractions were examined by immunoblot analysis using mAb 21-9, which is directed against cancer cell-derived matriptase. Two bands of 95- and 110-kDa were detected as indicated; uncomplexed matriptase was not detected. In C, both pooled 110-kDa (lanes 1 and 2) and 95-kDa (lanes 3 and 4) fractions were incubated in 1×SDS sample buffer in the absence of reducing agents at room temperature (−boiling) or at 95° C. (+boiling) for 5 min. prior to SDS-PAGE and subjected to Western blotting using mAb 21-9. The 110-kDa protein had a reduced rate of migration after boiling; however, the 95-kDa protein was converted to uncomplexed matriptase after boiling.

FIG. 2: Immunoaffinity purification of matriptase complexes. The partially purified matriptase complex from ion-exchange chromatography (see FIG. 1) was loaded onto a mAb 21-9-Sepharose column. The bound proteins were eluted with glycine buffer, pH 2.4, and neutralized by addition of 2 M Trizma. The eluted proteins were incubated in 1×SDS sample buffer in the absence of reducing agents at room temperature (lane 1; −Boiling) or at 95° C. (lane 2; +Boiling) for 5 min. The samples were resolved by SDS-PAGE and stained by colloidal Coomassie. In some batches of purification, as described in the Examples, the 95-kDa matriptase complex was obtained as the major band. This 95-kDa complex was capable of being converted to uncomplexed matriptase and a 40-kDa doublet after boiling. In some other batches, in addition to the 95-kDa complex, a smaller complex with an apparent size of 85-kDa was also obtained (lane 1). This 85-kDa matriptase complex could also be converted to uncompleted matriptase and a 25-kDa band after boiling (lane 2). Molecular mass markers are indicated. BP-40 and BP-25, 40- and 25-kDa binding proteins, respectively.

FIG. 3: Diagonal gel electrophoresis of the 95-kDa matriptase complex showing evidence that this complex corresponds to the uncomplexed matriptase in association with its 40-kDa binding protein doublet. The 95-kDa matriptase complex from human milk was subjected to diagonal gel electrophoresis. In the first dimension (D), the 95-kDa matriptase complex, without boiling treatment, was resolved by SDS-PAGE. Then a gel strip was sliced out, boiled in 1×SDS sample buffer in the absence of reducing agents for 5 min., and electrophoresed on a second SDS-polyacrylamide gel. The proteins were stained by colloidal Coomassie. After this procedure, the 95-kDa matriptase complex disappeared from the diagonal line and was converted to matriptase and a 40-kDa binding protein doublet (BP-40). The uncomplexed matriptase was observed on the diagonal line, as expected, suggesting that its migration rate was not changed by boiling.

FIG. 4: Structural characterization of matriptase complexes by monoclonal antibodies that are directed against the matriptase and its binding protein. A, a panel of mAbs was produced using the milk-derived matriptase complexes as immunogens. These mAbs were characterized by immunoblot analysis using the preparation containing both 95- and 85-kDa matriptase complexes described in the legend to FIG. 2. The matriptase preparation was dissolved in 1×SDS sample buffer in the absence of reducing agents and incubated at room temperature (lanes 1, 3, and 5; −Boiling) or at 95° C. (lanes 2, 4, and 6, +Boiling) for 5 min. Among these mAbs, an anti-matriptase mAb (M92) and two anti-binding protein mAbs (M58 and M19) are presented here. mAb M92 recognized both 95- and 85-kDa matriptase complexes under non-boiling conditions (lane 5) and interacted with the dissociated matriptase after boiling (lane 6), but not with the 40- and 25-kDa bands after boiling. Anti-binding protein mAb M19 recognized both 95- and 85-kDa complexes under non-boiling conditions (lane 3) and both 40- and 25-kDa bands after boiling (lane 4). Another mAb, M58, recognized only the 95-kDa matriptase complex (not the 85-kDa complex) under non-boiling conditions (lane 1); this mAb also detected the 40-kDa band, but not the 25-kDa band or the dissociated matriptase (lane 2). B, shown is a summary of the structures of matriptase-containing complexes and mAbs that are directed against these complexes and their subunits. BP-40 and BP-25, 40- and 25-kDa binding proteins, respectively.

FIG. 5: Amino acid sequence comparison of the binding protein and the inhibitor of human hepatocyte growth factor activator (HAI-1). Twelve-amino acid (GPPPAPPGLPAG) and seven-amino acid (TQGFGGS) sequences of the amino termini obtained from the 40-kDa binding protein doublet and the 25-kDa binding protein, respectively, and were identical to amino acids 36-47 and 154-160 of HAI-1. In addition, 12 unique peptides from the tryptic digest of the larger band of the 40-kDa binding protein doublet were compared with HAI-1 by MALDI-MS. These peptides covered 87 residues that spanned positions 135-310, or 17% of the entire HAI-1. The two stretches of amino-terminal protein sequences are double-underlined, and those 12 peptides identified by MALDI-MS, including residues 135-143, 154-164, 165-172, 173-182, 173-190, 183-190, 194-199, 203-214, 204-214, 288-301, and 302-310, are underlined.

FIG. 6: Western blot analysis of HAI-1 protein expressed in COS-7 cells using anti-binding protein mAb M19. The HAI-1 cDNA fragment that was generated by reverse transcriptase-polymerase chain resection and that contains the entire coding region was inserted into the expression vector pcDNA3.1 and transfected into COS-7 cells. Cell lysates from HAI-1-transfected COS-7 cells (lane 2), COS-7 cells (lane 3), and matriptase-transfected COS-7 cells (lane 1), and the 2 M KCl-washed membrane fraction of T-47D human breast cancer cells (lane 4) were subjected to Western blot analysis using anti-binding protein mAb M19.

FIG. 7: Expression analysis of matriptase and its complexes in human foreskin fibroblasts, fibrosarcoma and immortalized mammary luminal epithelial cells. Total released proteins in the serum-free conditioned medium of each cell line were collected and concentrated. Total protein (3 μg of protein/lane) was incubated in 1×SDS sample buffer in the absence of reducing agents at room temperature (−Boiling) or at 95° C. (+Boiling), subjected to SDS-PAGE, transferred to polyvinylidene fluoride (PVDF) membrane, and probed by anti-matriptase mAb 21-9. Lanes 1 (HS27) and 2 (HS68) are human foreskin fibroblasts. Lane 3 is HT-1080 fibrosarcoma cells. Lanes 4-11 are four milk-derived, SV40-immortalized luminal epithelial cells: MTSV-1.1B (lanes 4 and 5); MTSV-1.7 (lanes 6 and 7); MRSV-4.1 (lanes 8 and 9); and MRSV-4.2 (lanes 10 and 11). In addition to uncomplexed matriptase, various levels of 95- and 110-kDa complexes were seen in non-boiled samples, but disappeared by boiling treatment, in conjunction with increased matriptase.

FIG. 8: Purification of matriptase in its 95-kDa complexed form from human milk. The partially purified 95-kDa matriptase complex from ion-exchange chromatography was loaded onto a mAb 21-9-Sepharose column. The bound proteins were eluted by glycine buffer, pH 2.4, and neutralized by addition of 2 M Trizma. The eluted proteins were incubated in 1×SDS sample buffer in the absence of reducing agents at room temperature (lanes 1; −Boil) or at 95° C. (lanes 2, +Boil) for 5 min. The samples were resolved by SDS-polyacrylamide gel electrophoresis and either stained by colloidal Coomassie (A) or subjected to immunoblot analysis using mAb 21-9 (B) or gelatin zymography (C). The 95-kDa matriptase complex was eluted from this affinity column as the major protein (A, lane 1); it was recognized by mAb 21-9 (B, lane 1); and it also exhibited gelatinolytic activity (C, lane 1). The 95-kDa matriptase complex was converted to matriptase by boiling (A, lane 2). The gelatinolytic activity of the 95-kDa protease was destroyed by boiling, but a low level of the gelatinolytic activity was survived and converted to matriptase (C, lane 2). A low level of uncomplexed matriptase was co-purified with the 95-kDa matriptase complex by affinity chromatography (A, lane 1); it also exhibited gelatinolytic activity (C, lane 1). Immunoblot analysis enhanced the signal of the uncompleted matriptase and reconfirmed its existence (B, lane 1). Several other polypeptides were also seen (A, lanes 1 and 2). Some of them could be the degraded products of the protease since they were recognized by mAb 21-9 after longer exposure to the x-ray film. A 40-kDa protein doublet was seen in low levels in a non-boiled sample (A, lane 1), but its levels were increased after boiling (A, lane 2). This 40-kDa doublet was not recognized by mAb 21-9 (B). We propose that these two polypeptides could be binding proteins (BPs) of matriptase. The sizes of the molecular mass markers are indicated.

FIG. 9: The nucleotide and deduced amino acid sequences (SEQ ID NO: 3) of a matriptase cDNA clone. The primers (20 bases at the 5′-end and 18 bases at the 3′-end) used for reverse transcriptase-polymerase chain reaction are underlined. Thirty-three bases beyond the 5′-end primer and 92 bases beyond the 3′-end primer were taken from SNC19 cDNA and incorporated. The cDNA sequence (SEQ ID NO: 1) was translated from the fifth ATG codon in the open reading frame. Nucleotide and amino acid numbers are shown on the left. Sequences that agreed with the internal sequences obtained from matriptase are double-underlined. His-484, Asp-539, and Ser-633 are boxed and indicated the putative catalytic triad of matriptase. Potential N-glycosylation sites an indicated (Δ). An RGD sequence is indicated (

).

FIG. 10: Comparison of the amino acid sequence of the C-terminal region of matriptase with trypsin, chymotrypsin, and with the catalytic domains of other serine proteases. The C-terminal region (amino acids 431-683) of matriptase is compared with human trypsin (Emi et al., Gene (Amnst.) 41: 305-10 (1986)); human chymotrypsin (Tomita et al., Biochem. Biophys. Res. Commun. 158: 569-75 (1989)); the catalytic chains of human enteropeptidase (Kitamoto et al., Proc. Natl. Acad. Sci. USA 91: 7588-92 (1994)), human hepsin (Leytus et al., Biochemistry 27: 1067-74 (1988)), human blood coagulation factor XI (Fujikawa et al., Biochemistry 25: 2417-24 (1986)), and human plasminogen; and the serine protease domains of two transmembrane serine proteases, human TMPRSS2 (Paoloni-Giacobino et al., Genomics 44: 309-20 (1997)) and the Drosophila Stubble-stubbloid gene (Sb-sbd) (Appel et al., Proc. Natl. Acad. Sci. USA 90: 4937-41 (1993)). Gaps to maximize homologies are indicated by dashes. Residues in the catalytic triads (matriptase His-484, Asp-539, and Ser-633) are boxed and indicated (▴). The conserved activation motif ((R/K)VIGG) is boxed, and the proteolytic activation site is indicated. Eight conserved cysteines needed to form four intramolecular disulfide bonds are boxed, and the likely pairings are as follows: Cys-469-Cys-485, Cys-604-Cys-618, Cys-629-Cys-658, and Cys-432-Cys-559. The disulfide bond Cys-432-Cys-559. The disulfide bond Cys-432-Cys-559 is observed in two-chain serine proteases, but not in trypsin and chymotrypsin. Residues in the substrate pocket (Asp-627, Gly-655, and Gly-665) are boxed and indicated (

). It is evident that the residue positioned at the bottom of the substrate pocket is Asp in trypsin-like proteases, including matriptase, but Ser in chymotrypsin.

FIG. 11: Alignment of partial sequences of the noncatalytic domain with those of homologous regions in other proteins. A, the cysteine-rich repeats of matriptase (amino acids 280-314, 315-351, 352-387, and 394-430) are compared with the consensus sequences of the human LDL receptor (Sudhof et al., Science 228: 815-22 (1985)), LDL receptor-related protein (LRP) (Herz et al., EMBO J. 7: 4119-27 (1988)), human perlecan (Murdoch et al., J. Biol. Chem. 267: 8544-57 (1992)), and rat GP-300 (Raychowdhury et al., Science 244: 1163-65 (1989)). The consensus sequences are boxed. B, C1r/s-type sequences of matriptase (Mt; amino acids 42-155 and 168-268) are compared with selected domains of human complement subcomponent C1r (amino acids 193-298) (Leytus et al., Biochemistry 25: 4855-63 (1986); Journet, Biochem. J. 240: 783-87 (1986)), C1s (amino acids 175-283) (Mackinnon et al., Eur. J. Biochem. 169: 547-53 (1987); and Tosi et al., Biochemistry 26: 8516-24 (1987)), Ra-reactive factor (RaRF) (amino acids 185-290) (Takada et al., Biochem. Biophys. Res. Commun. 196: 1003-9 (1993); and Sato et al., Int. Immunol. 6: 665-9 (1994)), and a calcium dependent serine protease (CSP) (amino acids 181-289) (Kinoshita et al., FEBS Lett. 250: 411-5 (1989)). The consensus sequences are boxed.

FIG. 12: Shows the domain structure of matriptase. A schematic representation of the structure of matriptase is presented. The protease consists of 683 amino acids, and the protein product has a calculated mass of 75,626 Da. The protease contains two tandem complement subcomponent C1r and C1s domains and four tandem LDL receptor domains. The serine protease domain is at the carboxyl terminus.

FIG. 13: Inhibition of matriptase by HAI-1. Matriptase and HAI-1 were isolated from human milk by anti-matriptase mAb 21-9 immunoaffinity chromatography, as described in Example 1, and were maintained in an uncomplexed status in elution buffer, 0.1 M glycine, pH 2.4. This preparation was brought to pH 8.5, incubated at 37° C. for 0, 5, 30, and 60 min., and subjected to immunoblotting using anti-matriptase mAb 21-9 (panel A), gelatin zymography (panel B), and to a cleavage rate assay using the synthetic, fluorescent substrate, BOC-Gln-Ala-Agr-7-amido 4-methylcoumarin (panel C). At 0 min., matriptase was detected in its uncomplexed form (panel A), exhibiting strong gelatinolytic activity (panel B), and cleavage of soluble substrate at rapid rate (panel C). After 5 min incubation at 37° C., matriptase was detected both in an uncomplexed and complexed form (panel A); the uncomplexed matriptase exhibited gelatinolytic activity, while much weaker activity was observed for complexed matriptase (panel B); the cleavage rate for fluorescent substrate was significantly reduced, down to 18% (panel C). After 30 and 60 min. incubations, matriptase was detected mainly in an complexed form (panel A); negligible activity was observed by gelatin zymography (panel B) and by cleavage of fluorescent substrate. A milk-derived, matriptase-related 110-kDa protease (as indicated in panel A), which was not a complex of matriptase and HAI-1, and whose migration on SDS gel was reduced after boiling (see Example 1).

FIG. 14: Schematic representation of processing and interaction of matriptase and its cognate inhibitor. Both matriptase and its cognate inhibitor are likely to be biosynthesized as integral membrane proteins. “TM” indicates the location of the transmembrane domain. “I” stands for Kunitz domain 1; “II” for Kunitz domain 2; and “L” stands for LDL receptor domain.

FIG. 15: Nucleic acid sequence for human matriptase (SEQ ID NO: 2). SEQ ID NO: 2 contains additional nucleic acid sequence encoding the first 172 amino acids located in the amino-terminus of the encoded protein as compared to SEQ ID NO: 1, which is a truncated form of matriptase. SEQ ID NO:2 represents the full-length form of the nucleic acid encoding matriptase, whereas SEQ ID NO: 1 is a truncated form. The sequence can be found at GenBank Accession No. AF118224.

FIG. 16: Amino acid sequence for human matriptase (SEQ ID NO: 4). This sequence contains 855 amino acids, which is larger than the sequence described in Lin et al., J. Biol. Chem. 274:18231-6 (1999) (SEQ ID NO: 2). SEQ ID NO: 4 is the full length form of the matriptase protein, whereas SEQ ID NO: 3 is a truncated matriptase protein lacking 172 amino acids at the amino terminus. The protein sequence can be found at GenBank Accession No. AAD42765.

FIG. 17: Production of mAbs which are specifically directed against active, two-chain form of matriptase. This Western blot compares the affinities of monoclonal antibodies M130 (lanes 1 and 2), M123 (lanes 3, 4, 7 and 8), M32 (lanes 5 and 6), and M69 (lanes 9 and 10) to different forms of matriptase.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the invention to provide a method of preventing and treating malignancies, pre-malignant conditions, and other conditions in a subject which are characterized by the presence of a single-chain (zymogen) and/or two-chain (activated) form of matriptase in a biological sample comprising the step of administering an amount of a matriptase modulating agent capable of preventing or treating the malignancy, the pre-malignant lesion, or other condition.

It is another object of the invention to provide matriptase inhibitors, such as a Bowman Birk inhibitor (BBI) or structurally related molecules or fragments thereof.

Another object of the invention is to provide nucleic acid molecules (SEQ ID NOS: 1 and 2) encoding matriptase proteins or polypeptide fragments thereof (SEQ ID NOS: 3 and 4).

It is a further object of the invention to provide an antibody or antibodies which recognizes and binds to SEQ ID NO: 3 or a fragment thereof, SEQ ID NO: 4 or a fragment thereof, to a single-chain (zymogen) form of matriptase or to a two-chain (active) from of matriptase. Preferred antibodies are monoclonal antibodies and fragments thereof as well as chimeric, humanized or human antibodies.

It is also an object of the invention to provide a method of inhibiting tumor onset, tumor growth, and invasion or tumor metastasis, or other pathologic conditions, by administering an agent which inhibits or modulates activation of the zymogen form of matriptase or the activity of the two-chain (active) form of matriptase expressed by a tumor cell on a cell of other pathologic conditions. One preferred agent is BBIC, fragments thereof, or structurally related inhibitors (e.g., structurally related serine protease inhibitors).

Another object of the invention is a method of identifying a compound that specifically binds to a single-chain or a two-chain form of matriptase comprising the steps of: (A) exposing a single-chain or two-chain form of matriptase to a compound; (B) determining whether the single-chain or two-chain form of matriptase specifically binds to the compound; and (C) determining whether the compound that binds to the single-chain form of matriptase inhibits activation to the two-chain form of matriptase, or whether the compound binds to the two-chain form of matriptase and inhibits its catalytic activity.

It is a further object of the invention to disclose a method of diagnosing in vivo the presence of a pre-malignant lesion, a malignancy, or other pathologic condition in a subject comprising the steps of: (A) administering a labeled agent to a subject which recognizes and binds to a single-chain or two-chain form of matriptase; and (B) imaging the subject for the localization of the labeled agent.

It is a further object of the invention to diagnose in vitro the presence of a pre-malignant lesion, a malignancy, or other pathologic conditions in a subject comprising the steps of: (A) obtaining a biological sample from a subject that is to be tested for a pre-malignant lesion, a malignancy, or other pathologic condition; (B) exposing the biological sample to a labeled agent which recognizes and binds to the single-chain form and/or the two-chain form of matriptase; and (C) determining whether said labeled agent bound to the biological sample.

Another object of the invention is to provide a method of identifying a compound that specifically binds to a single-chain or a two-chain form of matriptase comprising the steps of: (A) identifying by molecular modeling whether the compound could bind to the activation site on the single-chain form of matriptase, the catalytic site of the two-chain form of matriptase, the C1r/C1s domain of either form of matriptase, or other regulatory domain of the molecule; (B) exposing a single-chain form or two-chain form of matriptase to the compound; (C) determining whether the compound binds to the single-chain form or the two-chain form of matriptase; and (D) if the compound binds to a form of matriptase, further determining whether the compound inhibits activation of the single-chain form of matriptase to a two-chain form of matriptase, whether the compound binds to the two-chain form of matriptase and inhibits its catalytic activity, whether the compound binds to the C1r/C1s domain, and thereby inhibits dimerization of the protein, or whether the compound binds to another regulatory domain of matriptase thereby modulating activation of matriptase or a matriptase activity.

DETAILED DESCRIPTION OF THE INVENTION

Matriptase is a trypsin-like serine protease with two regulatory modules: two tandem repeats of the complement subcomponent C1r/s domain and four tandem repeats of LDL receptor domain (Lin et al., J. Biol. Chem. 274: 18231-6 (1999)). In order to evaluate the role of matriptase in physiological conditions, its expression in human milk was studied. It was found that milk-derived matriptase strongly interacts with fragments of HAI-1 to form SDS-stable complexes.

The mosaic protease is characterized by trypsin-like activity and two regulatory modules (e.g., LDL receptor and complement subcomponent C1r/s domains), was initially purified from T-47D human breast cancer cells.

In breast cancer cells, matriptase was detected mainly as an uncomplexed form; however, low levels of matriptase were detected in SDS-stable, 110- and 95-kDa complexes that could be dissociated by boiling. In striking contrast, only the complexed matriptase was detected in human milk. The complexed matriptase has now been purified by a combination of ionic exchange chromatography and immunoaffinity chromatography. Amino acid sequences obtained from the matriptase-associated proteins reveal that they are fragments of an integral membrane, Kunitz-type serine protease inhibitor that was previously reported to be an inhibitor (termed HAI-1) of hepatocyte growth factor activator. In addition, matriptase and its complexes were also detected in four milk-derived, SV-40 T-antigen-immortalized mammary luminal epithelial cell lines, but not in two human foreskin fibroblasts nor in HT1080 fibrosacroma cell line. The milk-derived matriptase complexes are likely to be produced by the epithelial components of lactating mammary gland in vivo, and the activity and function of matriptase may be differentially regulated by its cognate inhibitor, comparing breast cancer with the lactating mammary gland.

A. DEFINITIONS

By “matriptase” is meant a trypsin-like protein, with a molecular weight of between 72-kDa and 92-kDa and is related to SEQ ID NO: 4 or is a fragment thereof. It can include both single-chain and double-chain forms of the protein. The zymogen form (inactive form) of matriptase is a single-chain protein. The two-chain form of matriptase is the active form of matriptase, which possesses catalytic activity. Both forms of matriptase are found to some extent in milk and cancer cells because extracellular matrix (ECM) remodeling is necessary to both normal and pathologic remodeling processes. FIG. 14 displays all known forms of matriptase. Both cancer cells and milk contain the different forms of matriptase. However, in milk the dominant form is the activated form of matriptase which then binds to HAI-1.

By “matriptase modulating compound” or “matriptase modulating agent” is meant a reagent which regulates, preferably inhibits the activation of matriptase (e.g., cleavage of the matriptase single-chain zymogen to the active two-chain moiety) or the activity of the two-chain form of matriptase. This inhibition can be at the transcriptional, translation, and/or post-translational levels. Additionally, modulation of matriptase activity can be via the binding of a compound to the zymogen or activated forms of matriptase.

By “matriptase expressing tissue” is meant any tissue which expresses any form of matriptase, either malignant, pre-malignant, normal tissue, or tissue which is subject to another pathologic condition

By “BBI” is meant compounds known as Bowman-Birk inhibitors, including those from soybeans as described by Birk, Int. J. Pept. Protein Res. 25: 113-21 (1985). BBIs have been isolated from leguminous plants and have a molecular weight of about 8,000 to 20,000 Daltons and include, but are not limited to, for example: BBI inhibitors of Dolichos bifloros and Macrotyloma uniflorum seeds, BBI inhibitors of Torresea cearensis seeds, BBI inhibitors of winter pea seeds, DgTI, and BBI-like inhibitors of sunflower seeds (Prakash et al., J. Mol. Biol. 235: 364-6 (1994); Tanaka et al., Biol. Chem. 378: 273-81 (1997); Quillien et al., J. Protein Chem. 16: 195-203 (1997); Bueno et al., Biochem. Biophys. Res. Commun. 261: 838-43 (1999); and Luckett et al., J. Mol. Biol. 290: 525-33 (1999)). BBI-like inhibitors are those with sequence and conformational similarity with the trypsin-reactive loop of the Bowman-Birk family of serine protease inhibitors. BBIs and BBI-like inhibitors can include any isoforms.

By “BBIC” is meant a concentrate of BBI or biologically active fragments thereof that inhibit matriptase activity (e.g., amino acid substituted protease inhibitory loops). The BBIC concentrate will preferably contain an amount of BBI ranging from 0.00001 to at least about 0.1 mg/ml. Preferably the BBIC will be administered in dosage sufficient to obtain a blood level of 0.001 to 1 mM concentration of BBI in the blood as a means of inhibiting tumor initiation in, for example, a subject susceptible to breast cancer as indicated by the presence of matriptase and/or matriptase complexes in nipple aspirate or other biological fluid, or in tissue from biopsy, including tissue from a needle biopsy.

By “malignancy” is meant to refer to a tissue, cell or organ which contains a neoplasm or tumor that is cancerous as opposed to benign. Malignant cells typically involve growth that infiltrates tissue (e.g., metastases). By “benign” is meant an abnormal growth which does not spread by metastasis or infiltration of the tissue. The malignant cell of the instant invention can be of any tissue; preferred tissues are epithelial cells.

By “tumor invasion” or “tumor metastasis” is meant the ability of a tumor to develop secondary tumors at a site remote from the primary tumor. Tumor metastasis typically requires local invasion, passive transport, lodgement and proliferation at a remote site. This process also requires the development of tumor vascularization, a process termed angiogenesis. Therefore, by “tumor invation” and “metastasis,” we also include the process of tumor angiogenesis.

By “pre-malignant conditions” or “pre-malignant lesion” is meant a cell or tissue which has the potential to turn malignant or metastatic, and preferably epithelial cells with said potential. Pre-malignant lesions include, but are not limited to: atypical ductal hyperplasia of the breast, actinic keratosis (AK), leukoplakia, Barrett's epithelium (columnar metaplasia) of the esophagus, ulcerative colitis, adenomatous colorectal polyps, erythroplasia of Queyrat, Bowen's disease, bowenoid papulosis, vulvar intraepithelial neoplasia (VIN), and displastic changes to the cervix.

By “other condition” or “pathologic conditions” is meant any genetic susceptibility or non-cancerous pathologic condition relating to any disease susceptibility or diagnosis.

By “tumor formation-inhibiting effective amount” is meant an amount of a compound, which is characterized as inhibiting activation of matriptase or matriptase activity, and which when administered to a subject, such as a human subject, prevents the formation of a tumor, or causes a preexisting tumor, or pre-malignant condition, to enter remission. This can be assessed by screening a high-risk patient for a prolonged period of time to determine that the cancer does not arise and/or the pre-malignant condition is reversed. This also can be assessed by imaging of the subject with a tumor to determine whether the mass of the tumor is shrinking. A tumor formation-inhibiting effective amount also includes an amounts which provides ameliorative to relief to the subject. The tumor formation-inhibiting effective amount can also be assessed based on its effect on blood circulation of inhibitors, such as BBIC. Preferred tumor formation-inhibiting effective amounts of agents such as BBIC are in the range of 100 μg/kg to 20 mg/kg body weight of the subject. More preferred ranges include 1 μg/kg to 10 mg/kg body weight of the subject.

By “labeling agent” is meant to include fluorescent labels, enzyme labels, and radioactive labels. By “radiolabel” or “radioactive label” is meant any radioisotope for use in humans for purposes of diagnostic imaging. Preferred radioisotopes for such use include: ⁶⁷Cu, ⁶⁷Ga, ⁹⁹Te, ¹³¹I, ¹²³I, ¹²⁵I, ¹¹¹In, ¹⁸⁸Re, ¹⁸⁶Re and ⁹⁰Y. By “fluorescent label” is meant any compound used for screening samples (e.g., tissue samples and biopsies) which emits fluorescent energy. Preferred fluorescent labels include fluorescein, rhodamine and phycoerythrin.

By “biological sample” is meant a specimen comprising body fluids, cells or tissue from a subject, preferably a human subject. Preferably the biological sample contains cells, which can be obtained via a biopsy or a nipple aspirate, or are epithelial cells. The sample can also be body fluid that has come into contact, either naturally or by artificial methods (e.g. surgical means), a malignant cell or cells of a pre-malignant lesion.

By “matriptase expressing tissue” is meant any biological sample comprising one or more cells which expresses a form or forms of matriptase.

By “subject” is meant an animal, preferably mammalian, and most preferably human.

As used herein, the term “antibody” is meant to refer to complete, intact antibodies, and Fab fragments and F(ab)₂ fragments thereof. Complete, intact antibodies include monoclonal antibodies such as murine monoclonal antibodies (mAb), chimeric antibodies and humanized antibodies. The production of antibodies and the protein structures of complete, intact antibodies, as well as antibody fragments (e.g., Fab fragments and F(ab)₂ fragments) and the organization of the genetic sequences that encode such molecules are well known and are described, for example, in Harlow et al., ANTIBODIES: A LABORATORY MANUAL, Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y. (1988).

By “immunogenic fragment” is meant a portion of a matriptase protein which induces humoral and/or cell-mediated immunity but not immunological tolerance.

By “epitope” is meant a region on an antigen molecule (e.g., matriptase) to which an antibody or an immunogenic fragment thereof binds specifically. The epitope can be a three dimensional epitope formed from residues on different regions of a protein antigen molecule, which, in a native state, are closely apposed due to protein folding. “Epitope” as used herein can also mean an epitope created by a peptide or hapten portion of matriptase and not a three dimensional epitope.

B. NUCLEIC ACID MOLECULES

The present invention further provides nucleic acid molecules that encode the protein having SEQ ID NO: 3 or SEQ ID NO: 4, or fragments thereof, and related proteins, which are preferably in isolated form. As used herein, “nucleic acid” is defined as RNA or DNA that encodes a peptide as defined above, or is complementary to nucleic acid sequence encoding such peptides, or hybridizes to such nucleic acid and remains stably bound to it under appropriate stringency conditions, or encodes a polypeptide sharing at least 75% sequence identity, preferably at least 80%, and more preferably at least 85%, with the peptide sequences. Specifically contemplated are genomic DNA, cDNA, mRNA and antisense molecules, as well as nucleic acids based on alternative backbone or including alternative bases whether derived from natural sources or synthesized.

“Stringent conditions” are those that (1) employ low ionic strength and high temperature for washing, for example, 0.015 M NaCl, 0.0015 M sodium titrate, 0.1% SDS at 50° C.; or (2) employ during hybridization a denaturing agent such as formamide, for example, 50% (vol/vol) formamide with 0.1% bovine serum albumin, 0.1% Ficoll, 0.1% polyvinylpyrrolidone, 50 mM sodium phosphate buffer at pH 6.5 with 750 mM NaCl, 75 mM sodium citrate at 42° C. Another example is use of 50% formamide, 5×SSC (0.75 M NaCl, 0.075 M sodium citrate), 50 mM sodium phosphate (pH 6.8), 0.1% sodium pyrophosphate, 5×Denhardt's solution, sonicated salmon sperm DNA (50 μg/ml), 0.1% SDS, and 10% dextran sulfate at 42° C., with washes at 42° C. in 0.2×SSC and 0.1% SDS. A skilled artisan can readily determine and vary the stringency conditions appropriately to obtain a clear and detectable hybridization signal.

As used herein, a nucleic acid molecule is said to be “isolated” when the nucleic acid molecule is substantially separated from contaminant nucleic acid encoding other polypeptides from the source of nucleic acid.

The present invention further provides fragments of the BBI nucleic acid coding sequence. As used herein, a fragment of a BBI coding sequence refers to a truncated version of the entire protein encoding sequence. The size of the fragment will be determined by the intended use. For example, if the fragment is chosen so as to encode an active portion of the protein, the fragment will need to be large enough to encode the functional region(s) of the protein. If the fragment is to be used as a nucleic acid probe or PCR primer, then the fragment length is chosen so as to obtain a relatively small number of false positives during probing/priming.

Fragments of the nucleic acid molecules of the present invention (i.e., synthetic oligonucleotides) that are used as probes or specific primers for the polymerase chain reaction (PCR), or to synthesize gene sequences encoding proteins of the invention can easily be synthesized by chemical techniques, for example, the phosphotriester method of Matteucci et al., J. Am. Chem. Soc. 103: 3185-91 (1981) or using automated synthesis methods. In addition, larger DNA segments can readily be prepared by well known methods, such as synthesis of a group of oligonucleotides that define various modular segments of the gene, followed by ligation of oligonucleotides to build the complete modified gene.

The BBI nucleic acid molecules of the present invention may further be modified so as to contain a detectable label for diagnostic and probe purposes. A variety of such labels are known in the art and can readily be employed with the encoding molecules herein described. Suitable labels include, but are not limited to, biotin, radiolabeled nucleotides and the like. A skilled artisan can employ any of the art known labels to obtain a labeled encoding nucleic acid molecule.

Modifications to the primary structure itself by deletion, addition, or alteration of the amino acids incorporated into the protein sequence during translation can be made without destroying the activity of the protein. Such substitutions or other alterations result in proteins having an amino acid sequence encoded by a nucleic acid falling within the contemplated scope of the present invention.

C. ISOLATION OF OTHER RELATED NUCLEIC ACID MOLECULES

As described above, the identification of the human nucleic acid molecule having SEQ ID NO: 1 or SEQ ID NO: 2 allows a skilled artisan to isolate nucleic acid molecules that encode other members of the matriptase family, in addition to the human sequence herein described. Further, the presently disclosed nucleic acid molecules allow a skilled artisan to isolate nucleic acid molecules that encode other members of the matriptase family of proteins in addition to the disclosed protein having SEQ ID NO: 3 and SEQ ID NO: 4.

Essentially, a skilled artisan can readily use the amino acid sequence of NO: 3 or SEQ ID NO: 4 to generate antibody probes to screen expression libraries prepared from appropriate cells. Typically, polyclonal antiserum from mammals, such as rabbits, immunized with the purified protein (as described below) or monoclonal antibodies can be used to probe a mammalian cDNA or genomic expression library, such as λgtll library, to obtain the appropriate coding sequence for other members of the protein family. The cloned cDNA sequence can be expressed as a fusion protein, expressed directly using its own control sequences, or expressed by constructions using control sequences appropriate to the particular host used for expression of the enzyme.

Alternatively, a portion of the coding sequence herein described can be synthesized and used as a probe to retrieve DNA encoding a member of the protein family from any mammalian organism. Oligomers containing approximately preferredly 18-20 nucleotides or more (encoding about a 6-7 amino acid stretch) are prepared and used to screen genomic DNA or cDNA libraries to obtain hybridization under stringent conditions or conditions of sufficient stringency to eliminate an undue level of false positives.

Additionally, pairs of oligonucleotide primers can be prepared for use in a polymerase chain reaction (PCR) to selectively clone an encoding nucleic acid molecule. A PCR denature/anneal/extend cycle for using such PCR primers is well known in the art and can readily be adapted for use in isolating other encoding nucleic acid molecules.

D. rDNA MOLECULES CONTAINING A NUCLEIC ACID MOLECULE

The present invention further provides recombinant DNA molecules (rDNAs) that contain a coding sequence. As used herein, a rDNA molecule is a DNA molecule that has been subjected to molecular manipulation in situ. Methods for generating rDNA molecules are well known in the art, for example, see Sambrook et al., (1989). In the preferred rDNA molecules, a coding DNA sequence is operably linked to expression control sequences and/or vector sequences.

The choice of vector and/or expression control sequences to which a matriptase-encoding sequence of the present invention is operably linked depends directly, as is well known in the alt, on the functional properties desired, e.g., protein expression, and the host cell to be transformed. A vector contemplated by the present invention is at least capable of directing the replication or insertion into the host chromosome, and preferably also expression, of the structural gene included in the rDNA molecule.

Expression control elements that are used for regulating the expression of an operably linked protein encoding sequence are known in the art and include, but are not limited to, inducible promoters, constitutive promoters, secretion signals, and other regulatory elements. Preferably, the inducible promoter is readily controlled, such as being responsive to a nutrient in the host cell's medium.

In one embodiment, the vector containing a coding nucleic acid molecule will include a prokaryotic replicon, i.e., a DNA sequence having the ability to direct autonomous replication and maintenance of the recombinant DNA molecule extrachromosomally in a prokaryotic host cell, such as a bacterial host cell, transformed therewith. Such replicons are well known in the art. In addition, vectors that include a prokaryotic replicon may also include a gene whose expression confers a detectable marker such as a drug resistance. Typical bacterial drug resistance genes are those that confer resistance to ampicillin or tetracycline.

Vectors that include a prokaryotic replicon can further include a prokaryotic or bacteriophage promoter capable of directing the expression (transcription and translation) of the coding gene sequences in a bacterial host cell, such as E. coli. A promoter is an expression control element formed by a DNA sequence that permits binding of RNA polymerase and transcription to occur. Promoter sequences compatible with bacterial hosts are typically provided in plasmid vectors containing convenient restriction sites for insertion of a DNA segment of the present invention. Typical of such vector plasmids are pUC8, pUC9, pBR322 and pBR329 available from Biorad Laboratories, (Richmond, Calif.), and pPL and pKK223 available from Pharmacia, Piscataway, N.J.

Expression vectors compatible with eukaryotic cells, preferably those compatible with vertebrate cells, can also be used to form a rDNA molecules the contains a coding sequence. Eukaryotic cell expression vectors are well known in the art and are available from several commercial sources. Typically, such vectors are provided containing convenient restriction sites for insertion of the desired DNA segment. Typical of such vectors are pSVL and pKSV-10 (Pharmacia), pBPV-1/pML2d (International Biotechnologies, Inc.), pTDT1 (ATCC, #31255), the vector pCDM8 described herein, and the like eukaryotic expression vectors.

Eukaryotic cell expression vectors used to construct the rDNA molecules of the present invention may further include a selectable marker that is effective in an eukaryotic cell, preferably a drug resistance selection marker. A preferred drug resistance marker is the gene whose expression results in neomycin resistance, i.e., the neomycin phosphotransferase (neo) gene (Southern et al., J. Mol. Anal. Genet. 1: 327-341 (1982)). Alternatively, the selectable marker can be present on a separate plasmid, and the two vectors are introduced by cotransfection of the host cell, and selected by culturing in the appropriate drug for the selectable marker.

E. HOST CELLS CONTAINING AN EXOGENOUSLY SUPPLIED CODING NUCLEIC ACID MOLECULE

The present invention further provides host cells transformed with a nucleic acid molecule that encodes a protein of the present invention. The host cell can be either prokaryotic or eukaryotic. Eukaryotic cells useful for expression of a protein of the invention are not limited, so long as the cell line is compatible with cell culture methods and compatible with the propagation of the expression vector and expression of the gene product. Preferred eukaryotic host cells include, but are not limited to, yeast, insect and mammalian cells, preferably vertebrate cells such as those from a mouse, rat, monkey or human cell line. Preferred eukaryotic host cells include Chinese hamster ovary (CHO) cells available from the ATCC as CCL61, NIH Swiss mouse embryo cells NIH/3T3 available from the ATCC as CRL 1658, baby hamster kidney cells (BHK), and the like eukaryotic tissue culture cell lines (e.g., not breast cell lines).

Any prokaryotic host can be used to express a rDNA molecule encoding a protein of the invention. The preferred prokaryotic host is E. coli.

Transformation of appropriate cell hosts with a rDNA molecule of the present invention is accomplished by well known methods that typically depend on the type of vector used and host system employed. With regard to transformation of prokaryotic host cells, electroporation and salt treatment methods are typically employed, see, for example, Cohen et al., Proc. Natl. Acad. Sci. USA 69: 2110 (1972); and Maniatis et al., MOLECULAR CLONING, A LABORATORY MANUAL, Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y. (1982). With regard to transformation of vertebrate cells with vectors containing rDNAs, electroporation, cationic lipid or salt treatment methods are typically employed, see, for example, Graham et al., Virol. 54: 536-9 (1973); and Wigler et al., Proc. Natl. Acad. Sci. USA 76: 1373-6 (1979).

Successfully transformed cells, i.e., cells that contain a rDNA molecule of the present invention, can be identified by well known techniques including the selection for a selectable marker. For example, cells resulting from the introduction of an rDNA of the present invention can be cloned to produce single colonies. Cells from those colonies can be harvested, lysed and their DNA content examined for the presence of the rDNA using a method such as that described by Southern, J. Mol. Biol. 98: 503-17 (1975) or the proteins produced from the cell assayed via an immunological method.

F. PRODUCTION OF RECOMBINANT PROTEINS USING A rDNA MOLECULE

The present invention further provides methods for producing a protein of the invention (e.g., matriptase) using nucleic acid molecules herein described. In general terms, the production of a recombinant form of a matriptase protein typically involves the following steps:

First, a nucleic acid molecule is obtained that encodes a protein of the invention, such as the nucleic acid molecule depicted in SEQ ID NOS: 1 or 2, or particularly for the matriptase nucleotides encoding for example, the serine protease catalytic domain in the carboxy terminus of the matriptase protein or the LDL domain. The coding sequence is directly suitable for expression in any host, as it is not interrupted by introns. The sequence can be transfected into host cells such as eukaryotic cells or prokaryotic cells. Eukaryotic hosts include mammalian cells (e.g., HEK293 cells, CHO cells and PAE-PDGF-R cells), as well as insect cells such as Sf9 cells using recombinant baculovirus. Alternatively, fragments encoding only portion of matriptase can be expressed alone or as a fusion protein. For example, the C-terminus of matriptase containing the serine protease domain can be expressed in bacteria as a GST- or His-tag fusion protein. These fusion proteins can then purified and used to generate polyclonal antibodies.

The nucleic acid molecule is then preferably placed in operable linkage with suitable control sequences, as described above, to form an expression unit containing the protein open reading frame. The expression unit is used to transform a suitable host and the transformed host is cultured under conditions that allow the production of the recombinant protein. Optionally the recombinant protein is isolated from the medium or from the cells; recovery and purification of the protein may not be necessary in some instances where some impurities may be tolerated.

Each of the foregoing steps can be done in a variety of ways. For example, the desired coding sequences may be obtained from genomic fragments and used directly in appropriate hosts. The constriction of expression vectors that are operable in a variety of hosts is accomplished using appropriate replicons and control sequences, as set forth above. The control sequences, expression vectors, and transformation methods are dependent on the type of host cell used to express the gene and were discussed in detail earlier. Suitable restriction sites can, if not normally available, be added to the ends of the coding sequence so as to provide an excisable gene to insert into these vectors. A skilled artisan can readily adapt any host/expression system known in the art for use with the nucleic acid molecules of the invention to produce recombinant protein.

G. METHODS TO IDENTIFY BINDING PARTNERS

Another embodiment of the present invention provides methods for use in isolating and identifying binding partners of matriptase proteins. In detail, a protein of the invention is mixed with a potential binding partner or an extract or fraction of a cell under conditions that allow the association of potential binding partners with the protein of the invention. After mixing, peptides, polypeptides, proteins or other molecules that have become associated with a protein of the invention are separated from the mixture. The binding partner that bound to the protein of the invention can then be removed and further analyzed. To identify and isolate a binding partner, the entire protein, for instance the entire disclosed protein of SEQ ID NO: 3 or SEQ ID NO: 4 can be used. Alternatively, a fragment of the protein can be used.

As used herein, a cellular extract refers to a preparation or fraction which is made from a lysed or disrupted cell.

A variety of methods can be used to obtain cell extracts. Cells can be disrupted using either physical or chemical disruption methods. Examples of physical disruption methods include, but are not limited to, sonication and mechanical shearing. Examples of chemical lysis methods include, but are not limited to, detergent lysis and enzyme lysis. A skilled artisan can readily adapt methods for preparing cellular extracts in order to obtain extracts for use in the present methods.

Once an extract of a cell is prepared, the extract is mixed with the protein of the invention under conditions in which association of the protein with the binding partner can occur. A variety of conditions can be used, the most preferred being conditions that closely resemble conditions found in the cytoplasm of a human cell. Features such as osmolarity, pH, temperature, and the concentration of cellular extract used, can be varied to optimize the association of the protein with the binding partner.

After mixing under appropriate conditions, the bound complex is separated from the mixture. A variety of techniques can be utilized to separate the mixture. For example, antibodies specific to a protein of the invention can be used to immunoprecipitate the binding partner complex. Alternatively, standard chemical separation techniques such as chromatography and density/sediment centrifugation can be used.

After removing the non-associated cellular constituents in the extract, the binding partner can be dissociated from the complex using conventional methods. For example, dissociation can be accomplished by altering the salt concentration or pH of the mixture.

To aid in separating associated binding partner pairs from the mixed extract, the protein of the invention can be immobilized on a solid support. For example, the protein can be attached to a nitrocellulose matrix or acrylic beads. Attachment of the protein or a fragment thereof to a solid support aids in separating peptide/binding partner pairs from other constituents found in the extract. The identified binding partners can be either a single protein or a complex made up of two or more proteins.

Alternatively, the nucleic acid molecules of the invention can be used in a yeast two-hybrid system. The yeast two-hybrid system has been used to identify other protein partner pairs and can readily be adapted to employ the nucleic acid molecules herein described.

One preferred in vitro binding assay for matriptase would comprise a mixture of a polypeptide comprising at least the matriptase serine catalytic domain for and one or more candidate binding targets or substrates. After incubating the mixture under appropriate conditions, one would determine whether matriptase or a polypeptide fragment thereof containing the catalytic domain binds with the candidate substrate. For cell-free binding assays, one of the components usually comprises or is coupled to a label. The label may provide for direct detection, such as radioactivity, luminescence, optical or electron density, etc., or indirect detection such as an epitope tag, an enzyme, etc. A variety of methods may be employed to detect the label depending on the nature of the label and other assay components. For example, the label may be detected bound to the solid substrate or a portion of the bound complex containing the label may be separated from the solid substrate, and the label thereafter detected.

H. METHODS TO IDENTIFY AGENTS THAT MODULATE THE EXPRESSION A NUCLEIC ACID ENCODING THE MATRIPTASE

Another embodiment of the present invention provides methods for identifying agents that modulate the expression of a nucleic acid encoding a protein of the invention, such as a protein having the amino acid sequence of SEQ ID NO: 3 or SEQ ID NO: 4. Such assays may utilize any available means of monitoring for changes in the expression level of the nucleic acids of the invention. As used herein, an agent is said to modulate the expression of a nucleic acid of the invention, for instance a nucleic acid encoding the protein having the sequence of SEQ ID NO: 3 or SEQ ID NO: 4, if it is capable of up- or down-regulating expression of the nucleic acid in a cell.

In one assay format, cell lines that contain reporter gene fusions between the open reading frame of matriptase or of SEQ ID NOS: 1 or 2 and any assayable fusion partner may be prepared. Numerous assayable fusion partners are known and readily available including the firefly luciferase gene and the gene encoding chloramphenicol acetyltransferase (Alam et al., Anal. Biochem. 188: 245-54 (1990)). Cell lines containing the reporter gene fusions are then exposed to the agent to be tested under appropriate conditions and time. Differential expression of the reporter gene between samples exposed to the agent and control samples identifies agents which modulate the expression of a nucleic acid encoding the protein having the sequence of SEQ ID NO: 3 or SEQ ID NO: 4 or related proteins.

Additional assay formats may be used to monitor the ability of the agent to modulate the expression of a nucleic acid encoding a protein of the invention such as the protein having SEQ ID NO: 3 or SEQ ID NO: 4. For instance, mRNA expression may be monitored directly by hybridization to the nucleic acids of the invention. Cell lines are exposed to the agent to be tested under appropriate conditions and time and total RNA or mRNA is isolated by standard procedures such those disclosed in Sambrook et al. (MOLECULAR CLONING: A LABORATORY MANUAL, 2nd Ed. Cold Spring Harbor Laboratory Press, 1989). Probes to detect differences in RNA expression levels between cells exposed to the agent and control cells may be prepared from the nucleic acids of the invention. It is preferable, but not necessary, to design probes which hybridize only with target nucleic acids under conditions of high stringency. Only highly complementary nucleic acid hybrids form under conditions of high stringency. Accordingly, the stringency of the assay conditions determines the amount of complementarity which should exist between two nucleic acid strands in order to form a hybrid. Stringency should be chosen to maximize the difference in stability between the probe:target hybrid and potential probe:non-target hybrids.

Probes may be designed from the nucleic acids of the invention through methods known in the art. For instance, the G+C content of the probe and the probe length can affect probe binding to its target sequence. Methods to optimize probe specificity are commonly available, see, e.g., Sambrook et al. (1989) or Ausubel et al. (CURRENT PROTOCOLS IN M OLECULAR BIOLOGY, Greene Publishing Co., NY, 1995).

Hybridization conditions are modified using known methods, such as those described by Sambrook et al. (1989) and Ausubel et al. (1995), as required for each probe. Hybridization of total cellular RNA or RNA enriched for polyA RNA can be accomplished in any available format. For instance, total cellular RNA or RNA enriched for polyA RNA can be affixed to a solid support, and the solid support exposed to at least one probe comprising at least one, or part of one of the sequences of the invention under conditions in which the probe will specifically hybridize. Alternatively, nucleic acid fragments comprising at least one, or part of one of the sequences of the invention can be affixed to a solid support, such as a porous glass wafer. The glass wafer can then be exposed to total cellular RNA or polyA RNA from a sample under conditions in which the affixed sequences will specifically hybridize. Such glass wafers and hybridization methods are widely available, for example, those disclosed by Beattie (WO 95/11755). By examining for the ability of a given probe to specifically hybridize to an RNA sample from an untreated cell population and from a cell population exposed to the agent, agents which up or down regulate the expression of a nucleic acid encoding the protein having the sequence of SEQ ID NO: 3 or SEQ ID NO: 4 are identified.

I. METHODS TO IDENTIFY AGENTS THAT MODULATE AT LEAST ONE ACTIVITY OF THE MATRIPTASE

Another embodiment of the present invention provides methods for identifying agents that modulate at least one activity of a protein of the invention, such as the protein having the amino acid sequence of SEQ ID NO: 3 or SEQ ID NO: 4. Such methods or assays may utilize any means of monitoring or detecting the desired activity.

In one format, the relative amounts of a protein of the invention between a cell population that has been exposed to the agent to be tested compared to an unexposed control cell population may be assayed (e.g., breast cancer cell line). In this format, probes such as specific antibodies are used to monitor the differential expression of the protein in the different cell populations. Cell lines or populations are exposed to the agent to be tested under appropriate conditions and time. Cellular lysates may be prepared from the exposed cell line or population and a control, unexposed cell line or population. The cellular lysates are then analyzed with the probe.

For example, N- and C-terminal fragments of matriptase can be expressed in bacteria and used to search for proteins which bind to these fragments. Fusion proteins, such as His-tag or GST fusion to the N- or C-terminal regions of matriptase can be prepared for use as a matriptase fragment substrate. These fusion proteins can be coupled to, for example, Glutathione-Sepharose beads and then probed with cell lysates. Prior to lysis, the cells may be treated with a candidate agent which may modulate matriptase or proteins that interact with domains on matriptase. Lysate proteins binding to the fusion proteins can be resolved by SDS-PAGE, isolated and identified by protein sequencing or mass spectroscopy, as is known in the art.

Antibody probes are prepared by immunizing suitable mammalian hosts in appropriate immunization protocols using the peptides, polypeptides or proteins of the invention if they are of sufficient length (e.g. 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30, 35, 40 or more consecutive amino acids of a matriptase protein), or if required to enhance immunogenicity, conjugated to suitable carriers. Methods for preparing immunogenic conjugates with carriers, such as bovine serum albumin (BSA), keyhole limpet hemocyanin (KLH), or other carrier proteins are well known in the art. In some circumstances, direct conjugation using, for example, carbodiimide reagents may be effective; in other instances linking reagents such as those supplied by Pierce Chemical Co., Rockford, Ill., may be desirable to provide accessibility to the hapten. Hapten peptides can be extended at either the amino or carboxy terminus with a Cys residue or interspersed with cysteine residues, for example, to facilitate linking to a carrier. Administration of the immunogens is conducted generally by injection over a suitable time period and with use of suitable adjuvants, as is generally understood in the art. During the immunization schedule, titers of antibodies are taken to determine adequacy of antibody formation.

Anti-peptide antibodies can be generated using synthetic peptides corresponding to, for example, the carboxy terminal amino acids of matriptase. Synthetic peptides can be as small as 1-3 amino acids in length, but are preferably at least 4 or more amino acid residues long. The peptides can be coupled to KLH using standard methods and can be immunized into animals, such as rabbits or ungulate. Polyclonal anti-matriptase peptide antibodies can then be purified, for example using Actigel beads containing the covalently bound peptide.

While the polyclonal antisera produced in this way may be satisfactory for some applications, for pharmaceutical compositions, use of monoclonal preparations is preferred. Immortalized cell lines which secrete the desired monoclonal antibodies may be prepared using the standard method of Kohler et al., (Nature 256: 495-7 (1975)) or modifications which effect immortalization of lymphocytes or spleen cells, as is generally known. The immortalized cell lines secreting the desired antibodies are screened by immunoassay in which the antigen is the peptide hapten, polypeptide or protein. When the appropriate immortalized cell culture secreting the desired antibody is identified, the cells can be cultured either in vitro or by production in vivo via ascites fluid. Of particular interest, are monoclonal antibodies which recognize the catalytic domain of matriptase (e.g., amino acids 432-683 of SEQ ID NO: 3).

Additionally, the zymogen or two-chain forms of matriptase can be utilized to make monoclonal antibodies which recognize conformation epitopes. For peptide-directed monoclonal antibodies, peptides from the C1r/C1s domain can be used to generate anti-C1r/C1s domain monoclonal antibodies which can thereby block activation of the zymogen to the two-chain form of matriptase. This domain can similarly be the substrate for other non-antibody compounds which bind to these preferred domains on either the single-chain or double-chain forms of matriptase and thereby modulate the activity of matriptase or prevent its activation.

The desired monoclonal antibodies are then recovered from the culture supernatant or from the ascites supernatant. Fragments of the monoclonals or the polyclonal antisera which contain the immunologically significant portion can be used as antagonists, as well as the intact antibodies. Use of immunologically reactive fragments, such as the Fab, Fab′, of F(ab′)₂ fragments are often preferable, especially in a therapeutic context, as these fragments are generally less immunogenic than the whole immunoglobulin.

The antibodies or fragments may also be produced, using current technology, by recombinant means. Regions that bind specifically to the desired regions of receptor can also be produced in the context of chimeras with multiple species origin.

Agents that are assayed in the above method can be randomly selected or rationally selected or designed. As used herein, an agent is said to be randomly selected when the agent is chosen randomly without considering the specific sequences involved in the association of the a protein of the invention alone or with its associated substrates, binding partners, etc. An example of randomly selected agents is the use a chemical library or a peptide combinatorial library, or a growth broth of an organism.

As used herein, an agent is said to be rationally selected or designed when the agent is chosen on a non-random basis which takes into account the sequence of the target site and/or its conformation in connection with the agent's action. As described in the Examples, there are proposed binding sites for serine protease and (catalytic) sites in the protein having SEQ ID NO: 3 or SEQ ID NO: 4. Agents can be rationally selected or rationally designed by utilizing the peptide sequences that make up these sites. For example, a rationally selected peptide agent can be a peptide whose amino acid sequence is identical to the ATP or calmodulin binding sites or domains.

The agents of the present invention can be, as examples, peptides, small molecules, and carbohydrates. A skilled artisan can readily recognize that there is no limit as to the structural nature of the agents of the present invention.

The peptide agents of the invention can be prepared using standard solid phase (or solution phase) peptide synthesis methods, as is known in the art. In addition, the DNA encoding these peptides may be synthesized using commercially available oligonucleotide synthesis instrumentation and produced recombinantly using standard recombinant production systems. The production using solid phase peptide synthesis is necessitated if non-gene-encoded amino acids are to be included.

Another class of agents of the present invention are antibodies immunoreactive with critical positions of proteins of the invention. Antibody agents are obtained by immunization of suitable mammalian subjects with peptides, containing as antigenic regions, those portions of the protein intended to be targeted by the antibodies.

J. PHARMACEUTICAL COMPOSITIONS

The present invention further includes agents which modulate matriptase activity in a cell formulated into a pharmaceutical composition. The pharmaceutical compositions of the invention include those suitable for oral, rectal, nasal, topical (including buccal and sublingual) or parenteral (including subcutaneous, intramuscular, intravenous and intradermal) administration. The formulations may conveniently be presented in unit dosage form, e.g., tablets and sustained release capsules, and in liposomes, and may be prepared by any methods well know in the art of pharmacy. See, for example, REMINGTON'S PHARMACEUTICAL SCIENCES (18^(th) ed., Mack Publ. Co. 1990).

Such preparative methods include the step of bringing into association with the molecule to be administered ingredients, such as the carrier, which constitutes one or more accessory ingredients. In general, the compositions are prepared by uniformly and intimately bringing into association the active ingredients with liquid carriers, liposomes or finely divided solid carriers or both, and then if necessary shaping the product.

Compositions of the present invention suitable for oral administration may be presented as discrete units such as capsules, cachets or tablets each containing a predetermined amount of the active ingredient; as a powder or granules; as a solution or a suspension in an aqueous liquid or a non-aqueous liquid; or as an oil-in-water liquid emulsion or a water-in-oil liquid emulsion, or packed in liposomes and as a bolus, etc.

A tablet may be made by compression or molding, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing in a suitable machine the active ingredient in a free-flowing form such as a powder or granules, optionally mixed with a binder, lubricant, inert diluent, preservative, surface-active or dispersing agent. Molded tablets may be made by molding in a suitable machine a mixture of the powdered compound moistened with an inert liquid diluent. The tablets may optionally be coated or scored and may be formulated so as to provide slow or controlled release of the active ingredient therein.

Compositions suitable for topical administration include lozenges comprising the ingredients in a flavored basis, usually sucrose and acacia or tragacanth; and pastilles comprising the active ingredient in an inert basis such as gelatin and glycerin, or sucrose and acacia.

Compositions suitable for parenteral administration include aqueous and non-aqueous sterile injection solutions which may contain anti-oxidants, buffers, bacteriostats and solutes, which render the formulation isotonic with the blood of the intended recipient; and aqueous and non-aqueous sterile suspensions, which may include suspending agents and thickening agents. The formulations may be presented in unit-dose or multi-dose containers, for example, sealed ampules and vials, and may be stored in a freeze dried (lyophilized) condition requiring only the addition of the sterile liquid carrier, for example water for injections, immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules and tablets.

Application of the pharmaceutical composition often will be local, so as to be administered at the site of interest. Various techniques can be used for providing the subject compositions at the site of interest, such as injection, use of catheters, trocars, projectiles, pluronic gel, stents, sustained drug release polymers or other device which provides for internal access.

It will be appreciated that actual preferred amounts of a pharmaceutical composition used in a given therapy will vary depending upon the particular form being utilized, the particular compositions formulated, the mode of application, the particular site of administration, the patient's weight, general health, sex, etc., the particular indication being treated, etc. and other such factors that are recognized by those skilled in the art including the attendant physician or veterinarian. Optimal administration rates for a given protocol of administration can be readily determined by those skilled in the art using conventional dosage determination tests.

Antibodies. The antibodies and immunogenic portions thereof of this invention are administered at a concentration that is therapeutically effective to prevent or treat any of the afore-mentioned disease states. To accomplish this goal, the antibodies may be formulated using a variety of acceptable excipients known in the art. Typically, the antibodies are preferably administered by injection, either intravenously or intraperitoneally. Methods to accomplish this administration are known to those of ordinary skill in the art. It may also be possible to obtain compositions which may be topically or orally administered, or which may be capable of transmission across mucous membranes.

Before administration to patients, formulants may be added to the antibodies. A liquid formulation is preferred. For example, these formulants may include oils, polymers, vitamins, carbohydrates, amino acids, salts, buffers, albumin, surfactants, or bulking agents. Preferably carbohydrates include sugar or sugar alcohols, such as mono-, di-, or polysaccharides, or water soluble glucans. The saccharides or glucans can include fructose, dextrose, lactose, glucose, mannose, sorbose, xylose, maltose, sucrose, dextran, pullulan, dextrin, alpha- and beta-cyclodextrin, soluble starch, hydroxyethyl starch and carboxymethylcellulose, or mixtures thereof. Sucrose is most preferred. “Sugar alcohol” is defined as a C4 to C8 hydrocarbon having an —OH group and includes galactitol, inositol, mannitol, xylitol, sorbitol, glycerol, and arabitol. Mannitol is most preferred. These sugars or sugar alcohols mentioned above may be used individually or in combination. There is no fixed limit to amount used, as long as the sugar or sugar alcohol is soluble in the aqueous preparation. Preferably, the sugar or sugar alcohol concentration is between 1.0 w/v percent and 7.0 w/v percent, more preferable between 2.0 and 6.0 w/v percent. Preferably amino acids include levorotary (L) forms of carnitine, arginine and betaine; however, other amino acids may be added. Preferred polymers include polyvinylpyrrolidone (PVP) with an average molecular weight between 2,000 and 3,000, or polyethylene glycol (PEG) with an average molecular weight between 3,000 and 5,000. It is also preferred to use a buffer in the composition to minimize pH changes in the solution before lyophilization or after reconstitution. Most any physiological buffer may be used, but citrate, phosphate, succinate, and glutamate buffers or mixtures thereof are preferred. Most preferred is a citrate buffer. Preferably, the concentration is from 0.01 to 0.3 molar. Surfactants that can be added to the formulation are shown in EP patent applications No. EP 0 270 799 and EP 0 268 110.

Additionally, antibodies can bc chemically modified by covalent conjugation to a polymer to increase their circulating half-life. Preferred polymers, and methods to attach them to peptides, are shown in U.S. Pat. Nos. 4,766,106; 4,179,337; 4,495,285; and 4,609,546. Preferred polymers are polyoxyethylated polyols and polyethylene glycol (PEG). PEG is soluble in water at room temperature and has the general formula: R(O—CH₂—CH₂)_(n)O—R where R can be hydrogen, or a protective group, such as an alkyl or alkanol group. Preferably, the protective group has between 1 and 8 carbons, more preferably it is methyl. The symbol “n” is a positive integer, preferably between 1 and 1,000, more preferably between 2 and 500. The preferred PEG ranges in molecular weight between 1,000 and 40,000, more preferably between 2,000 and 20,000, most preferably between 3,000 and 12,000. Preferably, PEG has at least one hydroxy group; more preferably it is a terminal hydroxy group. It is this hydroxy group which is preferably activated. However, it will be understood that the type and amount of the reactive groups may be varied to achieve a covalently conjugated PEG/antibody of the present invention.

Water soluble polyoxyethylated polyols are also useful in the present invention. They include polyoxyethylated sorbitol, polyoxyethylated glucose, polyoxyethylated glycerol (POG), etc. POG is preferred. One reason is because the glycerol backbone of polyoxyethylated glycerol is the same backbone occurring naturally in, for example, animals and humans in mono-, di-, triglycerides. Therefore, this branching would not necessarily be seen as a foreign agent in the body. The POG has a preferred molecular weight in the same range as PEG.

Another drug delivery system for increasing circulatory half-life is the liposome. Methods of preparing liposome delivery systems are discussed in Gabizon et al., Cancer Res. 42: 4734-9 (1982); Szoka et al., Annu. Rev. Biophys. Bioeng. 9: 467-508 (1980); Szoka et al., Meth. Enzymol. 149: 143-7 (1987); and Langner et al., Pol. J. Pharmacol. 51: 211-22 (1999). Other drug delivery systems are known in the art.

After the liquid pharmaceutical composition is prepared, it is preferably lyophilized to prevent degradation and to preserve sterility. Methods for lyophilizing liquid compositions are known to those of ordinary skill in the art. Just prior to use, the composition may be reconstituted with a sterile diluent (e.g., Ringer's solution, distilled water, or sterile saline) which may include additional ingredients. Upon reconstitution, the composition is preferably administered to subjects using those methods that are known to those skilled in the art.

As stated above, the antibodies and compositions of this invention are used preferably to treat human patients to prevent or treat any of the above-defined disease states. The preferred route of administration is parenterally. In parenteral administration, the compositions of this invention will be formulated in a unit dosage injectable form such as a solution, suspension or emulsion, in association with a pharmaceutically acceptable parenteral vehicle. Such vehicles are inherently nontoxic and non-therapeutic. Examples of such vehicles are saline, Ringer's solution, dextrose solution, and Hanks' solution. Non-aqueous vehicles such as fixed oils and ethyl oleate may also be used. A preferred vehicle is 5% dextrose in saline. The vehicle may contain minor amounts of additives such as substances that enhance isotonicity and chemical stability, including buffers and preservatives.

The dosage and mode of administration will depend on the individual. Generally, the compositions are administered so that antibodies are given at a dose between 1 μg/kg and 20 mg/kg, more preferably between 20 μg/kg and 10 mg/kg, most preferably between 1 and 7 mg/kg. Preferably, it is given as a bolus dose, to increase circulating levels by 10-20 fold and for 4-6 hours after the bolus dose. Continuous infusion may also be used after the bolus dose. If so, the antibodies may be infused at a dose between 5 and 20 μg/kg/minute, more preferably between 7 and 15 μg/kg/minute.

According to an equally preferred embodiment, the present invention relates to the use of a monoclonal antibody or a derivative thereof or a peptide, for the preparation of diagnostic or in vivo imaging means of any of the above-mentioned disease states.

According to a preferred embodiment an antibody, fragments, analogs, and derivatives thereof are detectably labeled through the use of halogen radioisotopes such as ¹³¹I, ¹²⁵I, metallic radionuclides ⁶⁷Cu, ¹¹¹In, ⁶⁷Ga, ⁹⁹Te, ¹³¹ I, ¹²³I, ¹⁸⁸ Re, 186 Re and ⁹⁰Y etc.; affinity labels (such as biotin, avidin, etc.), fluorescent labels, paramagnetic atoms, etc. and is provided to a patient to localize the site of infection or inflammation. Procedures for accomplishing such labeling are well known to those skilled in the art. Clinical application of antibodies in diagnostic imaging are reviewed by Laurino et al., Ann. Clin. Lab. Sci. 29: 158-66 (1999); Unger et al., Invest. Radiol. 20: 693-700 (1985), and Khaw et al., Science 209: 295-7 (1980).

The detection of foci of such detectably labelled antibodies is indicative of a metastatic disease, tumor development or a pre-malignant lesion with metastatic potential. In one embodiment, this examination for cancer is done by removing samples of tissue (e.g., biopsy), and incubating such samples in the presence of the detectably labeled antibodies. In a preferred embodiment, this technique is done in a non-invasive manner through the use of magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT) or fluorography and extracorporeal detecting means, etc. Such a diagnostic test may be employed in monitoring organ transplant recipients for early signs of potential tissue rejection. Such assays may also be conducted in efforts to determine an individual's predilection to rheumatoid arthritis or other chronic inflammatory diseases.

According to another embodiment the present invention relates to the use of a monoclonal antibody or a derivative thereof, as defined above for the preparation of diagnostic and in vivo imaging means of atherosclerosis.

K. MOLECULAR MODELING TO IDENTIFY COMPOUNDS THAT BIND MATRIPTASE

One method of identifying matriptase modulating compounds, and preferably matriptase inhibitors, is by using molecular modeling. Molecular modeling can be performed using the X-ray crystal structure of either the single-chain or two-chain forms of matriptase, or based on conformation information provided by the protein sequence. Specifically, as matriptase bears sequence homology to other trypsin-like molecules, the crystal structures of the other molecules (specifically trypsin) can be used to model matriptase domains. Specific sites to be targeted by inhibitors can then be studied using molecular modeling programs. Preferred sites include, but are not limited to: (1) the C1r/C1s dimerization domain on matriptase, (2) the activation site on the single-chain form of matriptase which is cleaved to form the two-chain form of matriptase, and (3) the catalytic domain of matriptase.

Molecules can be tested via molecular modeling programs to determine whether the can fit into one of the preferred sites on matriptase. Once molecules are identified which at least according to molecular modeling bind to a preferred domain, the molecules can be conveniently designed de novo by the help of three-dimensional molecular modeling computer software, such as the program called ALCHEMY-III (Tripos Associates Inc.; St. Louis, Mo.). In the case of peptide compounds, it is now possible to determine the influence and relative importance of specific amino acid residues on receptor or antigen binding, using such tools as magnetic resonance spectroscopy and molecular modeling, allowing the specific design and synthesis of peptides which bind a known antigen, antibody or receptor, or which mimic a known binding sequence or ligand.

Biological-Function Domain. The biological-function domain of the constructs is a structural entity within the molecule that binds the biological target and may either inhibition of activation of the single-chain matriptase to the two-chain, active form of matriptase or may inhibit the two-chain, active form of matriptase from binding to its normal substrate(s). For peptides which can form a ligand and receptor pair, in which the receptor is not a biological target, the discussions pertaining to a biological-function domain apply unless expressly limited to biological systems. The biological-function domain of the peptide includes the various amino acid side chains, arranged so that the domain binds stereospecifically to, for example, the activation site of matriptase or the proteolytic active site of matriptase in its active, two-chain form. The biological-function domain may be either be sychnological (with structural elements placed in a continuous sequence) or rhegnylogical (with structural elements placed in a discontinuous sequence), as such concepts are described generally in Schwyzer, Biopolymers 31: 875-792 (1991).

After purification, crystallization and isolation, the subject crystals may be analyzed by techniques known in the art. Typical analysis yield structural, physical, and mechanistic information about the peptides. As discussed above, X-ray crystallography provides detailed structural information that may be used in conjunction with widely available molecular modeling programs to arrive at the three-dimensional arrangement of atoms in the peptide.

Peptide modeling can be used to design a variety of agents capable of modifying the activity of the subject peptide. For example, using the three-dimensional structure of the active site, matriptase agonists and antagonists having complementary structures can be designed to block the biological activity of matriptase. Further, matriptase structural information is useful for directing design of proteinaceous or non-proteinaceous matriptase modulating agents, based on knowledge of the contact residues between the matriptase and its substrate.

Computer modeling can also be performed as described in Example 4, or using nuclear magnetic resonance (NMR) or X-ray methods (Fletterick et al., eds., “Computer Graphics and Molecular Modeling,” in Current Communications in Molecular Biology (Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y., 1986). Exemplary modeling programs include “Homology” by Biosym (San Diego, Calif.), “Biograf” by BioDesign, “Nemesis” by Oxford Molecular, “SYBYL™” and “Composer” by Tripos Associates, “CHARM” by Polygen (Waltham, Mass.), “AMBER” by University of California, San Francisco, and “MM2” and “MMP2” by Molecular Design, Ltd.

EXAMPLES Example 1 Purification and Characterization of a Complex Containing Matriptase and a Kunitz-Type Serine Protease Inhibitor

These data as described in Lin et al., J. Biol. Chem. 274(26): 18237-42 (1999), which investigates the role of matriptase under physiological conditions such as differentiation and lactation.

Cell lines and culture condition: Four milk-derived, immortalized luminal mammary epithelial cell lines (MTSV-1.1B, MTSV-1.7, MRSV-4.1, and MRSV-4.2) were a gift from Dr. J. Taylor-Papadimitriou (ICRF, London) (Bartek et al., Proc. Natl. Acad. Sci. USA 88: 3520-24 (1991)), and were maintained in modified Iscove's minimal essential medium (Biofluids, Rockville, Md.) supplemented with 10% fetal calf serum (GIBCO), bovine insulin at 10 μg/ml, hydrocortisone (Sigma) at 5 μg/ml, and antibiotics. Human foreskin fibroblasts and the fibrosarcoma cell line, HT-1080 (from American Type Culture Collection, ATCC) were maintained in modified Iscove's minimal essential medium supplemented with 10% fetal calf serum (GIBCO). To collect cell conditioned medium, monolayers of these cells at confluency were washed twice with phosphate-buffered saline (PBS) and were cultured for two days in the absence of the serum in modified Iscove's minimal essential medium supplemented with insulin/transferrin/selenium (Biofluids).

Identification and partial isolation of matriptase-related proteases from human milk: To isolate matriptase-related proteases, 1.5 liters of frozen human milk from Georgetown University Medical Center Milk Bank was thawed and centrifuged to remove the milk fat and insoluble debris. Ammonium sulfate powder was added to the milk with continuous mixing to 40% saturation, and allowed to precipitate in a cold room for at least 2 hours. Protein precipitates were obtained by centrifugation at 5,000×g for 20 min. The pellets were saved, and the supernatant was further precipitated by addition of ammonium sulfate powder to 60% saturation. The protein pellets were dissolved in water, and then dialyzed against 20 mM Tris-HCl, pH 8.0 for DEAE chromatography or against 10 mM phosphate buffer, pH 6.0 for CM chromatography. Insoluble debris was cleared by centrifugation, and the supernatant was divided into five batches. Each batch was loaded onto a DEAE Sepharose FF column (2.5×20 cm) (Pharmacia; Piscataway, N.J.), equilibrated with 20 mM Tris-HCl, pH 8.0. The column was washed with 10 column volumes of equilibration buffer. Bound material was eluted with a linear gradient from 0-1 M NaCl in DEAE equilibration buffer with a total volume of 500 ml. Fractions (14 ml) were collected and assessed by immunoblot using mAb 21-9. To perform CM chromatography, the 95-kDa fraction from DEAE chromatography or the precipitate derived directly from ammonium sulfate precipitation was dialyzed against 10 mM phosphate buffer, pH 6.0. Insoluble debris was cleared by centrifugation and the supernatant was loaded onto a CM Sepharose FF column (2.5×20 cm) (Pharmacia; Piscataway, N.J.), equilibrated with 10 mM phosphate buffer, pH 6.0. The column was washed with 10 column volumes of equilibration buffer. Bound material was eluted with a linear gradient from 0-0.5 M NaCl in 10-MM phosphate buffer, pH 6.0 with total volume of 500 ml. 14 Milliliter fractions were assessed by immunoblot using mAb 21-9.

Immunoaffinity chromatography: Preparation of an immunoaffinity column coupling mAb 21-9 to Sepharose 4B (5 mg of IgG/ml of beads) was performed using CNBr-activated Sepharose 4B, as previously described (Lin et al. J. Biol. Chem. 272: 9147-52 (1997)). Partially purified 95-kDa matriptase complex from DEAE or CM chromatography was loaded onto a 1-ml column at a flow rate of 7 ml/h. The column was washed with 1% Triton X-100 in PBS. Bound protease was then eluted using 0.1 M glycine-HCl (pH 2.4). Fractions were immediately neutralized using 2 M Trizma base.

Immunization and hybridoma fusion: Two six week old female Balb/c mice were immunized with matriptase complexes (10 μg per dose) at intervals of 2 weeks. Complete Freund's adjuvant was used for the initial immunizations, while incomplete adjuvant was used for boosts. Three days after the second boost, antiserum was collected from the tail vein, and the immunoresponse was determined by immunoblot. The final boost was conducted with the matriptase complex in the absence of adjuvant by tail vein injection. The splenocytes were collected and fused with mouse myoloma cells (SP2 or NS1) by polyethylene glycol (PEG) methodology, and the successful hybridoma cells were selected by HAT medium (Kilmartin et al., J. Cell. Biol. 93: 576-82 (1982)).

Hybridoma screening: The primary screening was carried out by western blot using the targets that contain a mixture of intact 95-kDa matriptase complex, dissociated matriptase, and the binding proteins. More than one hundred positive clones were selected in the primary screening. Three anti-matriptase mAbs (M32, M92, and M84) and two anti-binding protein mAbs (M 19 and M58) were selected and characterized in detail.

Monoclonal antibody preparation: To produce mAbs, hybridoma lines were gradually adapted to low serum-supplemented culture medium and then to protein free hybridoma medium (Gibco). Monoclonal antibodies were harvested and precipitated by 50% saturation with ammonium sulfate. Further purification was carried out by DEAE chromatography.

Immunoblotting analysis: Immunoblot was conducted as previously described (Lin et al., (1997)). Proteins were separated by 10% SDS-PAGE, transferred to polyvinylidene fluoride (PVDF), and probed with mAbs as specified. Immunoreactive polypeptides were visualized using peroxidase-labeled secondary antibody and the ECL detection system (Amersham Corp.; Arlington Heights, Ill.).

Diagonal SDS-PAGE: The 95-kDa matriptase complex preparation was resolved by SDS-PAGE under non-boiled conditions; the gel strip was sliced out, boiled in 1×SDS sample buffer, placed on an SDS-acrylamide gel without wells, and electrophoresed under the same conditions as the first dimension gel. Protein bands were stained by Colloidal Coomassie (Neuhoff et al., Electrophoresis 9: 255-62 (1988)), due to the negative image observed with silver stain.

Amino Acid Sequence analysis of the 40- and 25-kDa binding proteins: The 40- and 25-kDa binding proteins were purified as described above. The amino-terminal sequence of these proteins were determined (Matsudaira, J. Biol. Chem. 262: 10035-8 (1987)). Twelve (from 40-kDa protein) and seven (from 25-kDa protein) amino acid residues obtained were identical to the deduced amino acid sequences of an inhibitor of hepatocyte growth factor activator I (HAI-1) (Shimomura et al., J. Biol. Chem. 272: 6370-6 (1997)). To further confirm the identity of the binding protein to be HAI-1, the larger band from the 40-kDa protein doublet was subjected to in gel digestion and then to analysis by the matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) at HHMI Biopolymer Laboratory & W. M. Keck Foundation Biotechnology Resource Laboratory at Yale University.

Expression of HAI-1 in COS-7 cell: To verify that HAI-1 encodes the binding protein of matriptase, we isolated an HAI-1 cDNA fragment by reverse transcriptase-polymerase chain reaction (RT-PCR) utilizing mRNA from MTSV 1.1 B immortalized human luminal mammary epithelial cells. Primer sequences for HAI-1 (5′-GGCCCGCGCTCTGAAGGTGA-3′ and 5′-TTGGCAAGCAGGAAGCAGGG-3′) were derived from the published sequence. Standard RT-PCR was carried out using the Advantage RT-PCR kit (Clontech; Palo Alto, Calif.), and the product was ligated into pCR2.1 (Invitrogen; Carlsbad, Calif.) by TA cloning. The sequence of the RT-PCR product was obtained by standard methods, and confirmed with the published HAI-1 sequence (Miyazawa et al., J. Biol. Chem. 268: 10024-8 (1993)). An eukaryotic expression vector was constructed (pcDNA/HAI-1), utilizing the commercially available pcDNA3.1 vector (Invitrogen; San Diego, Calif.). A 1.6 kb EcoRI fragment containing the HAI-1 cDNA was cloned into the EcoRI site of pcDNA 3.1. This construct contains the open reading frame (ORF) of HAI-1 driven by a CMV promoter. Correct insertion of the HAI-1 cDNA was verified by restriction mapping. Transfections were performed using SuperFect transfection reagent (QIAGEN; Valencia, Calif.) as specified in manufacturer's handbook. After 48 hr, the HAI-1-transfected COS-7 cells were extracted with 1% Triton-X100 in 20 mM Tris-HCl pH 7.4.

Matriptase-related proteases in human milk: Previously, matriptase was observed to exist either in a major, uncomplexed form or in two minor SDS-stable (Lin et al., (1997)), complexed forms with apparent molecular masses of 110- and 95-kDa. The matriptase binding protein(s) was not identified. To identify these binding protein(s), we have examined the matriptase complexes found in human milk. Our hypothesis has been that the binding protein is a protease inhibitor and that its expression may be associated with a specific physiological status, such as differentiation or lactation. In human milk, two immunoreactive bands of 95- and 110-kDa in size, but no uncomplexed matriptase was detected by anti-matriptase mAb 21-9 under non-boiled and non-reduced conditions (FIG. 1). The 95-kDa band was the predominant species; the relative amount of the minor, 110-kDa band varied between different batches of milk (FIGS. 1A and B). In common with a 95-kDa immunoreactive matriptase complex previously identified in human breast cancer cells (Lin et al., (1997)), the milk-derived 95-kDa immunoreactive species was converted, after boiling in the absence of reducing agents, to a smaller immunoreactive band. This band corresponds in size to the previously described, uncomplexed matriptase from breast cancer (FIG. 1C). Thus, matriptase appeared to be a component of the 95-kDa complex, both in breast cancer cells and in milk. Although most of matriptase in breast cancer cells is uncomplexed, the opposite is true in milk.

Most of the minor, 110-kDa immunoreactive polypeptide in milk was precipitated by a 40% saturation of ammonium sulfate. This band was then separated from the major 95-kDa matriptase complex by DEAE chromatography (FIG. 1A). In contrast to the 95-kDa matriptase complex, the milk-derived 110-kDa immunoreactive polypeptide had a reduced rate of migration on an SDS-polyacrylamide gel after boiling (FIG. 1, panel C). These results suggest that this milk-derived 110-kDa immunoreactive polypeptide is not likely to be a protease complex. The 110-kDa species from breast cancer cells was converted by boiling into matriptase and another unidentified species (Lin et al., (1997)). This milk-derived 110-kDa species was thus distinct from the 110-kDa matriptase complex previously isolated from breast cancer T-47D cells.

Purification of matriptase complexes from human milk: The milk-derived 95-kDa matriptase complex has been isolated using an anti-matriptase mAb-21-9 immunoaffinity column. This highly purified 95-kDa matriptase complex can be converted to matriptase after boiling in conjunction with appearance of a protein doublet with apparent molecular mass of 40-kDa (Lin et at., J. Biol. Chem 274: 18231-6 (1999)). In some batches of milk, in addition to the 95-kDa complex, another protease complex doublet, with apparent molecular mass of 85-kDa, was also observed (FIG. 2, lane 1). Both 95- and 85-kDa matriptase complexes were converted to matriptase after boiling. In addition to matriptase, a 40-kDa and a 25-kDa protein bands were observed (FIG. 2, lane 2).

Biochemical and immunological approaches have been taken to prove the 40- and 25-kDa bands to be components of matriptase complexes. In our biochemical approach, a 95-kDa matriptase complex preparation, which also contains low levels of uncomplexed matriptase, was subjected to a non-boiling/boiling diagonal gel electrophoresis. In this gel electrophoresis system, proteins whose migration rate on an SDS polyacrylamide gel are not changed by boiling will be seen on the diagonal line. In contrast, heat-sensitive complexes will be dissociated into their constituent subunits and will be seen on the same electrophoretic path below the diagonal line; proteins whose configuration is changed by boiling resulting in a lower migration rate will be seen beyond the diagonal line. The sample was firstly resolved by SDS-PAGE and a strip of gel was sliced off. The sliced gel strip was boiled in 1×SDS sample buffer in the absence of reducing agents, placed on a second SDS polyacrylamide gel, and electrophoresed (FIG. 3). In the case of the 95-kDa matriptase complex, both the 40-kDa protein doublet and matriptase were observed below the diagonal line and on the same electrophoretic path (FIG. 3). This result thus confirmed that matriptase and the 40-kDa doublet were components of the 95-kDa protease complex. On the other hand, uncomplexed matriptase was seen on the diagonal line (FIG. 3).

In an immunological approach, a panel of mAbs was obtained using matriptase complexes as immunogens (FIG. 4). A new antimatriptase, antibody mAb M92, recognizes both 95- and 85-kDa matriptase complexes under non-boiling conditions (FIG. 4A, lane 5). This mAb recognizes uncomplexed matriptase, but not the 40- and 25-kDa bands after boiling, (FIG. 4A, lane 6). Monoclonal antibody, M19, recognizes both matriptase complexes under non-boiling conditions (FIG. 4A, lane 3), but not the uncomplexed matriptase under boiling conditions (FIG. 4A, lane 4). However, M19 detects both 40- and 25-kDa bands after boiling (FIG. 4A, lane 4).

A third antibody type, mAb M58, was also selected. This mAb selectively recognizes only the 95-kDa matriptase complex but not the 85-kDa complex under non-boiling conditions (FIG. 4A, lane 1); mAb M58 recognizes only the 40-kDa band but not the 25-kDa band after boiling, (FIG. 4A, lane 2). These results, combined with the results in FIG. 2, suggest that the 95-kDa matriptase complex is composed of matriptase and a 40-kDa component. The 85-kDa matriptase complex is composed of matriptase and the 25-kDa component. The 25-kDa component is likely to be a degraded product of the 40-kDa component. The epitope recognized by mAb M19 resides on both 40 and 25-kDa components, but the one recognized by mAb M58 resides only on the 40-kDa component. In FIG. 4 panel B, we summarize the structures of both 95- and 85-kDa matriptase complexes and their interactions with these mAbs.

The binding proteins of the matriptase are fragments of a Kunitz-type serine protease inhibitor: When the amino-terminal sequences of the 40- and 25-kDa binding proteins were determined, the sequences of the 40-kDa binding protein (e.g., GPPPAPPGLPAG) were found to be identical to the amino-terminal sequences of a Kunitz-type serine protease inhibitor (Shimomura et al., J. Biol. Chem. 272: 6370-76 (1997)), which was previously identified as an inhibitor of hepatocyte growth factor activator (HAI-1) (Shimomura et al., (1997)); the amino acid residues (e.g., TQGFGGS) obtained from the N-terminus of the 25-kDa binding protein are identical to the sequences from residue 154 through residue 160 of HAI-1 (Shimomura et al., (1997)). To further confirm that the binding proteins of matriptase are identifiable as HAI-1, the larger band from the 40-kDa doublet was subjected to in gel trypsin digestion. The tryptic digests were examined by matrix assisted laser desorption ionization mass spectrometry (MALDI-MS). Twelve unique peptides from the tryptic digests were matched to the HAI-1 sequence by searching the observed MALDI-MS masses from the binding protein to the HAI-1 (FIG. 5). These 12 peptides cover 87 residues that span residues 135-310. These results indicate that the binding proteins of matriptase are fragments of HAI-1.

In another study, the immunoreactivity of anti-binding protein mAb with HAI-1 that was expressed by HAI-1-transfected COS-7 cells (FIG. 6). Anti-binding protein mAb M19 detected a band with apparent size of 55-kDa in the cell lysate of HAI-1-transfected COS-7 cells (FIG. 6, lane 2) and in the 2 M KCl-washed membrane fraction of T-47D human breast cancer cells (FIG. 6, lane 4), but not in the COS-7 cells (FIG. 6, lane 3), nor in matriptase-transfected COS-7 cells (FIG. 6, lane 1). The immunoreactivity between anti-binding protein mAb and HAI-1 gene product provides a second line of evidence that the binding protein of matriptase is HAI-1. Because this size of the immunoreactive 55-kDa band is close to the calculated molecular mass (53,319 Da) of mature, membrane-bound HAI-1, and because its association with membrane fraction is sufficiently strong that it resists dissociation by washing with 2 M KCl, this 55-kDa band is considered likely to be the mature, intact HAI-1.

Mammary epithelial production of matriptase and the Kunitz-type protease inhibitor: To investigate the possible cell types which release matriptase and its complexes, we examined their expression in four milk-derived, Simian virus 40 large tumor antigen immortalized luminal epithelial cell lines (milk cells) (Bartek et al., Proc. Natl. Acad. Sci. USA 88: 3520-24 (1991)), two cultured human foreskin fibroblasts, and a fibrosarcoma cell line HT-1080 (FIG. 7). Positive results for the mammary luminal epithelial cells (FIG. 7, lanes 4-11) and negative results for the fibroblasts and HT-1080 fibrosarcoma cells (FIG. 7, lanes 1-3) suggest that the protease and its binding protein are produced by the epithelial components of the lactating mammary gland. In contrast to milk, the immortalized, mammary luminal epithelial cells expressed detectable, uncomplexed matriptase and an 110-kDa complex. This 110-kDa complex species was not detected in milk, but was detected in T-47D breast cancer cells (Lin et al., (1997)).

Example 2 Molecular Cloning and Characterization of Matriptase

This example describes the further isolation of matriptase protein and the gene encoding it as described by Lin et al., J. Biol. Chem. 274: 18231-6 (1999).

Cell lines and culture conditions: COS-7 cells were maintained in modified Iscove's minimal essential medium (Biofluids, Inc.; Rockville, Md.) supplemented with 5% fetal calf serum (Life Technologies, Inc.).

Purification of Matriptase: To obtain enough matriptase for amino acid sequencing, the enzyme was isolated from human mile (Lin et al., J. Biol. Chem. 274: 18237-42 (1999)). Briefly, human milk from the Georgetown University Medical Center Milk Bank was precipitated and collected by addition of ammonium sulfate between 40 and 60% saturation. Matriptase was purified by a combination of CM-Sepharose and immunoaffinity chromatography.

Amino Acid Sequence analysis: To obtain internal amino acid sequences, purified matriptase was separated by SDS-PAGE, lightly stained with Coomassie blue, and protein bands were excised. Matriptase was then subjected to in gel digestion and amino acid sequencing at HHMI Biopolymer Laboratory & W. M. Keck Foundation Biotechnology Resource Laboratory at Yale University. The aminoterminal sequences were determined as described previously (Matsudaira et al., J. Biol. Chem. 262: 10035-8 (1987)). Briefly, the proteins were resolved by SDS-PAGE, transferred to polyvinylidene difluoride membrane, and lightly stained with Coomassie blue. The proteins were excised and subjected to amino-terminal sequencing (Chemistry Department, Florida State University, Tallahassee, Fla.). The two short sequences obtained were identical to a deduced amino acid sequence termed SNC19 (GenBank Accession No. U20428).

Amplification of an SNC19 cDNA from T-47D breast cancer cells: An SNC19 cDNA clone was generated by reverse transcriptase-polymerase chain reaction (RT-PCR) utilizing mRNA from T-47D human breast cancer cells. Primer sequences for SNC19 (5′-CCTCCTCTTGGTCTTGCTGGGG-3′ and 5′-AGACCCGTCTGTTTTCCAGG-3′) were derived from the published sequence. Standard RT-PCR was conducted using the Advantage RT-PCR kit (Clontech; Palo Alto, Calif.). Products were analyzed on a 0.8% agarose gel and the resultant band of approximately 2.8 kb corresponding to the expected product size was excised from the gel, purified and ligated into pCR2.1 (Invitrogen, Carlsbad, Calif.) by TA cloning (pCR-SNC19).

Sequencing: DNA sequencing was performed on a Perkin Elmer Applied Biosystem automated 377 DNA sequencer (Foster City, Calif.) using standard methods with the assistance of the Lombardi Sequencing and Synthesis Shared Resource. The sequences were assembled and analyzed with Lasergene software for windows (DNA Star Inc.; Madison, Wis.). The predicted protein sequence was compared to sequences in Swiss-Prot© database at the National Center for Biotechnology Information using the BLAST network server.

Expression of SNC19 in COS-7 cell: To verify that SNC19 encodes the matriptase gene, we constructed an eukaryotic expression vector (pcDNA/SNC19) utilizing the commercially available pcDNA 3 vector (Invitrogen; San Diego, Calif.). A 2.83 kb EcoRI fragment containing the SNC19 cDNA was produced by digestion of pCR-SCN19 and cloned into the EcoRI site of pcDNA 3. This construct contains the open reading frame of SNC19 driven by a CMV promoter. Correct insertion of the SNC19 cDNA was verified by restriction mapping (data not shown). Transfections were carried out using SuperFect™ transfection reagent (QIAGEN; Valencia, Calif.), as specified in manufacturer's handbook. After 48 hr, the matriptase-transfected COS-7 cells and the control COS-7 cells, which were transfected with LacZ to monitor transfection efficiency, were extracted with 1% Triton-X100 in 20 mM Tris-HCl pH 7.4.

Immunoblotting analysis: Immunoblot was conducted as previously described (Lin et al., J. Biol. Chem. 272: 9147-52 (1997)). Proteins were separated by 100% SDS-PAGE, transferred to polyvinylidene fluoride membrane, and subsequently probed with anti-matriptase monoclonal antibody (mAB) M32. Immunoreactive polypeptides were visualized using peroxidase-labeled secondary antiserum and the ECL detection system (Amersham Corp.; Arlington Heights, Ill.).

Gelatin zymography: Gelatin zymography was carried out as previously described with some modifications (Brown et al., Biochem J. 101: 214-228 (1966)). Gelatin (1 mg/ml), as a substrate, was copolymerized with regular SDS-polyacryamide gel. Electrophoresis was performed at a constant current of 15 mA. The gelatin gels were washed 3 times with PBS containing 2% Triton X-100 and incubated in PBS at 37° C. overnight.

Cleavage of Synthetic Substrates: To demonstrate the trypsin-like activity of matriptase, various synthetic fluorescent protease substrates with arginine or lysine as the P1 site were tested with purified matriptase from human milk. Matriptase was assayed in 20 mM Tris buffer, pH 8.5, at 25° C. in a volume of 190 μl prior to addition to 10 μl of 2 mM substrate solution (to a final concentration of 0.1 mM). These substrates included t-butyloxycarbonyl (Boc)-Gln-Ala-Arg-7-amino-4-methylcoumarin (AMC), Box-benzyl-Glu-Gly-Arg-AMC, Boc-Leu-Gly-Arg-AMC, Boc-benzyl-Asp-Pro-Arg-AMC, Boc-Phe-Ser-Arg-AMC, Boc-Val-Pro-Arg-AMC, suceinyl-Ala-Phe-Lys-AMC, Boc-Leu-Arg-Arg-AMC, Boc-Gly, Lys-Arg-AMC, and Boc-Leu-Ser-Thr-Arg-AMC. These substrates were purchased from Sigma. The rate of cleavage of individual substrates was determined against time with a Hitachi F-4500 fluorescence spectrophotometer.

Results: In further studies, and referring specifically to FIG. 8, the partially purified 95-kDa matriptase complex from ion exchange chromatography was loaded onto a mAb 21-9-Sepharose column. The bound proteins were eluted by glycine buffer, pH 2.4, and neutralized by addition of 2 M Trizma base. The eluted proteins were incubated in 1×SDS sample buffer in the absence of reducing agents at room temperature (lanes 1, each panel, boiling−) or 95° C. (lanes 2, each panel, boiling+) for 5 min. The samples were resolved by SDS-PAGE and either stained by colloidal Coomassie (panel A), subjected to immunoblot analysis using mAb 21-9 (panel B), or subjected to gelatin zymography (panel C). The 95-kDa matriptase complex was eluted from this affinity column as the major protein (panel A, lane 1); it was recognized by mAb 21-9 (panel B, lane 1), and it also exhibited gelatinolytic activity (panel C, lane 1). The 95-kDa matriptase complex was converted to matriptase by boiling (panel A, lane 2). The gelatinolytic activity of the 95-kDa protease was destroyed by boiling, but a low level of the gelatinolytic activity survived and converted to matriptase (panel C, lane 2). A low level of uncomplexed matriptase was co-purified with the 95-kDa matriptase complex by affinity chromatography (panel A, lane 1); it also exhibited gelatinolytic activity (panel C, lane 1). Immunoblot analysis enhanced the signal of the uncomplexed matriptase and reconfirmed its existence (panel B, lane 1). Several other polypeptides were also seen (panel A, lanes 1 and 2). Some of them could be the degraded products of the protease, since they were recognized by mAb 21-9 after longer exposure to the X-ray film. A 40-kDa protein doublet was seen in low levels in a non-boiled sample (panel A, lane 1), but its levels were increased after boiling (panel A, lane 2). This 40-kDa doublet was not recognized by mAb 21-9 (panel B). We propose that these two polypeptides could be binding proteins of matriptase. In the figure, MW stands for the molecular weight markers; their sizes are as indicated.

Although sequence analysis of the 40-kDa binding protein has shown it to be a serine protease inhibitor (see below), some residual gelatinolytic activity was observed for the 95-kDa matriptase/inhibitor complex (FIG. 8 C). When matriptase and its binding protein were subjected to N-terminal sequencing, only 11 amino acid residues (VVGGTDADEGE) from matriptase were obtained with relatively low recovery and 12 amino acid residues (GPPPAPPGLPAG) were obtained from the amino-terminus of the 40-kDa binding protein have been obtained. The 11 amino acid residues from matriptase were identical to a deduced amino acid sequence from a 2.9 kb cDNA called SNC19 (accession number U20428). Numerous stop codons were observed in this deposited SNC19 sequence, resulting in several small, predicted translation products. Thus, a 2,830 bp cDNA fragment was obtained by reverse transcriptase-polymerase chain reaction using two primers based on the sequence of SNC19. There was extensive discrepancy (132 bases) between our sequence and that of SNC19.

Verification of SNC19 cDNA encoding matriptase: In addition to the sequence identity of matriptase with portion of SNC19, the immunoreactivity of anti-matriptase mAbs to the SNC19 gene product were examined to verify whether SNC19 encodes matriptase. SNC19 cDNA was inserted into the eukaryotic expression vector pcDNA3.1 and transfected into COS-7 monkey kidney fibroblasts, which do not express matriptase. A strong, immunoreactive band with the same size of matriptase from T-47D human breast cancer cells detected by anti-matriptase mAb M32 was observed in SNC-19 transfected COS-7 cells, but not in control COS-7 cells.

Nucleotide and predicted amino acid sequences of an matriptase cDNA clone: A nucleotide (SEQ ID NO: 1) and an amino acid sequences (SEQ ID NO: 3) of matriptase are shown in FIG. 9. The primers (20 bases at 5′ end and 18 bases at 3′ end) used for reverse transcriptase-polymerase chain reaction are underlined. Thirty three bases beyond the 51 end primer and 92 bases beyond 31 end primer were taken from SNC19 cDNA and incorporated. The cDNA sequence was translated from the fifth ATG (Met) codon in the open reading frame. Nucleotide and amino acid numbers are shown on the left. Double-underlines indicate sequences that agreed with the internal sequences obtained from matriptase. His-484, Asp-539 and Ser-633 were boxed and indicated the putative catalytic triad of matriptase. Potential N-glycosylation sites are indicated by Δ. A RGD sequence is indicated by

Matriptase cDNA is likely to be 2955 base pair long when the 5′ end 33 bases and the 3′ end 92 bases from SNC19 were added to the RT-PCR fragment (2,830 base pair long). The translation initiation site was assigned to the fifth methionine codon because the sequence GTCATGG matches a favorable Kozak consensus sequence (Kozak et al., Nucl. Acid. Res. 12: 857-72 (1984)). This methionine is followed by four positively charged amino acids and a 14 amino acid long hydrophobic region (Ser-18-Ser-31), a putative signal peptide. Assuming this methionine codon to be the initiator, the open reading frame was 2,049 base pairs long, and thus the deduced amino acid sequence was composed of 683 residues, with calculated molecular mass of 75,626. The two stretches of amino acid sequences (DYVEINGEK and VVGGTDADEGE) obtained from matriptase are located in aa 228-236 and aa 443-453; thus the translation frame is likely to be correct. There are three potential N-glycosylation sites with the canonical Asn-X-(Ser/Thr) and an RGD sequence. RGD sequence from proteins of the extracellular matrix has been found to mediate interactions with integrins (Ruoslahti et al., Science 238: 491-7 (1987)).

Structure of the matriptase catalytic domain: A homology search for the deduced amino acid sequence by BLAST in the Swiss-Prot© data base reveals that (1) the carboxyl-terminus at residue positions 432-683 of matriptase is homologous with other serine proteases; (2) matriptase contains the invariant catalytic triad; (3) matriptase contains a characteristic disulfide bond pattern; and (4) matriptase contains overall sequence similarity. Referring to FIG. 9, the primers (20 bases at 5′ end and 18 bases at 3′ end) used for reverse transcriptase-polymerase chain reaction are underlined. Thirty-three bases beyond the 5′ end primer and 92 bases beyond 3′ end primer were taken from SNC19 cDNA and incorporated. The cDNA sequence was translated from the fifth ATG codon in the open reading frame. Nucleotide and amino acid numbers are shown on the left. Double-underlines indicate sequences that agreed with the internal sequences obtained from matriptase. His-484, Asp-539, and Ser-633 were boxed and indicated the putative catalytic triad of matriptase. Potential N-glycosylation sites are indicated by Δ. A RGD sequence is indicated by

Compared with the archetype serine protease, chymotrypsin (Hartley et al., Biochem J. 101: 229-31 (1966); and Brown et al., Biochem J. 101: 214-28 (1966)) and other serine proteases, the three amino acids (His-484, Asp-539, and Ser-633) are likely to correspond to those in chymotrypsinogen (His-57, Asp-102, and Ser-195) and are likely to be essential for catalytic activity (Hartley et al., Nature 207: 1157-9 (1965)). The six most conserved cysteines needed to form three intramolecular disulfide bonds that stabilize the catalytic pocket have been determined in other chymotrypsin-related proteases. The most likely cysteine pairings in matriptase are: Cys-469-Cys-485, Cys-604-Cys-618, and Cys-629-Cys-658. Matriptase also contains two additional cysteines (Cys-432-Cys-559) which correspond to those used in two-chain proteases, such as enteropeptidase (Kitamoto et al, Proc. Natl. Acad. Sci. USA 91: 7588-92 (1994)), hepsin (Leytus et al., Biochemistry 27: 1067-74 (1988)) plasma kallikrein (Chung et al, Biochemistry 25: 2410-17 (1986)), blood coagulation factor XI (Fujikawa et al., Biochemistry 25: 2417-24 (1986)), and plasminogen (Forsgren et al., FEBS Lett. 213: 254-50 (1987)), but not in trypsin (Emi et al., Gene (Amst.) 41: 305-310 (1986)), or chymotrypsin (Tomita et al., Biochem., Biophys. Res. Commun. 158: 569-75 (1989)) (FIG. 10).

Referring more specifically to FIG. 10, the C-terminal region (aa 431-683) of matriptase is compared with human trypsin, human chymotrypsin, the catalytic chains of human enteropeptidase, human hepsin, human blood coagulation factor XI, and human plasminogen, and the serine protease domains of two transmembrane serine proteases, human TMPRSS2 and Drosophila Stubble-stubbloid gene (Sb-sbd). Residues are expressed in one letter code. Gaps to maximize homologies are indicated by residues in the catalytic triads (matriptase His-484, Asp-539, and Ser-633) were boxed and indicated by ♦. The conserved activation motif (R/KVIGG) was boxed and the proteolytic activation site was indicated. Eight conserved cysteines needed to form four intramolecular disulfide bonds are boxed, and the likely pairings are as follows: Cys-469-Cys-485, Cys-604-Cys-618, Cys-629-Cys-658, and Cys-432-Cys-559. The disulfide bond (Cys-432-Cys-559) is observed in two-chain serine proteases, but not in trypsin and chymotrypsin. Residues in the substrate pocket (Asp-627, Gly-655, and Gly-665) are boxed and indicated by

It is evident that the residue positioned at the bottom of substrate pocket is Asp in trypsin-like proteases, including matriptase, but is Ser in chymotrypsin.

A putative proteolytic activation site (Arg-442) of matriptase in a motif of Arg-Val-Val-Gly-Gly (RVVGG) is similar to the characteristic RIVGG motif in other serine proteases. However, the Ile residue is replaced by Val residue. This replacement is uncommon, but is observed in plasminogen. As mentioned above, a conserved intramolecular disulfide bond is found in those serine proteases that are synthesized as one-chain zymogens and are proteolytically activated to become active two chain forms. This disulfide bond is proposed to hold together the active catalytic fragment with their non-catalytic N-terminal fragments, thus serving as protein-protein interaction domain. This conserved intramolecular disulfide bond has been also observed in matriptase (Cys-432-Cys-559). These sequence analyses suggest that matriptase may be synthesized as a single chain zymogen and may become proteolytically activated to a two-chain form. If this is a case, the majority of matriptase in the conditioned medium of T-47D breast cancer cells is likely to be the zymogen; the active two-chain matriptase only represents a minor proportion, consistent with the purified matriptase from T-47D human breast cancer cells exhibiting an apparent size of 80-kDa under reduced conditions. This conclusion is also supported by the observation that the proposed N-terminal sequences for the catalytic chain of matriptase are identical to the stretch of amino acid sequences (VVGGTDADEGE), which were obtained with very low recovery when matriptase was subjected to N-terminal sequencing.

The substrate specificity (S₁) pocket of matriptase is likely to be composed of Asp-627 positioned at its bottom, with Gly-655 and Gly-665 at its neck, indicating that matriptase is a typical trypsin-like serine protease. Predicted preferential cleavage at amino acid residues with positively charged side chains was confirmed with various synthetic substrates with Arg and Lys residues as P1 sites (FIG. 11). Specifically, matriptase was able to cleave the following synthetic substrates, presented as follows, from the most rapid to the slowest: Boc-Gln-Ala-Arg-AMC, Boc-benzyl-Glu-Gly-Arg-AMC, Boc-Leu-Gly-Arg-AMC, Boc-benzyl-Asp-Pro-Arg-AMC, Boc-Phe-Ser-Arg-AMC, Boc-Leu-Arg-ArgAMC, Boc-Gly-Lys-Arg-AMC, and Boc-Leu-Ser-Thr-Arg-AMC. [Boc=t-butyloxycarbonyl; AMC=7-amino-4-methylcoumarin; LDL=low density lipoprotein]. This supports the view that matriptase prefers substrates with amino acid residues containing small side chains, such as Ala and Gly as P2 sites. These results suggest that matriptase, in analogy with trypsin, exhibits broad spectrum cleavage specificity. This broad spectrum cleavage activity is likely to be the explanation of its gelatinolytic activity. Its trypsin-like activity appears to be distinct from Gelatinases A and B, which may cleave gelatin at glycine residues, the most abundant (almost up to one third of) amino acid residues in gelatin.

Structure motifs of the noncatalytic region of matriptase: The non-catalytic region of matriptase contains two sets of repeating sequences, which may serve as a regulatory and/or binding domain for interaction with other proteins. Four tandem repeats of about 35 amino acids including 6 conserved cysteine residues (FIG. 12 A) were found at the amino terminal region (aa 280-430) of its serine protease domain. They are homologous with the cysteine-containing repeat of the LDL receptor (Sudhof et al., Science 228: 815-22 (1985)) and related proteins (Herz et al., EMBO J. 7: 4119-27 (1988)). All of these cysteine residues are likely be involved in disulfide bonds. In LDL receptor, the homologous, seven repeating sequences serve as the ligand binding domain. By analogy, the four tandem cysteine-containing repeats may also be the sites of interaction with other macromolecules. In addition, the cysteine-containing LDL receptor domain was found in other proteases, such as enteropeptidase (Matsushima et al., J. Biol. Chem. 269: 19976-82 (1994); and Kitamoto et al., Proc. Natl. Acad. Sci. USA 91: 7588-92 (1994)).

Referring to FIG. 12A, the cysteine-rich repeats of matriptase (aa 280-314, aa 315-351, aa 352-387, and aa 394-430) are compared with the consensus sequences of the human LDL receptor; LDL receptor-related protein (LRP); human perlecan; and rat GP-300. The consensus sequences are boxed. In FIG. 12B, C1r/s type sequences of matriptase (aa 42-155 and aa 168-268) are compared with selected domains of human complement subcomponent C1r (aa 193-298), C is (aa 175-283), Ra-reactive factor (RaRF) (aa 185290), and a calcium-dependent serine protease (CSP) (aa 181-289). The most consensus sequences are boxed.

The amino-terminal region of matriptase (aa 42-268) contains another two tandem segments with internal homology. These segments resemble partial sequences, originally identified in complement subcomponents C1r (Leytus et al., Biochemistry 25: 4855-63 (1986); and Journet et al., Biochem. J 240: 783-7 (1986)) and C1s (Mackinnon et al., Eur. J Biochem. 169: 547-53 (1987); and Tosi et al., Biochemistry 26: 8516-24 (1987)). This C1r/s domain was also found in other serine proteases, including Ra-reactive factor, a C4/C2-activating component, enteropeptidase, an activator of trypsinogen (Matsushima et al., (1994); Kitamoto et al., (1994)), and a calcium-dependent serine protease that is able to degrade extracellular matrix. These C1r/s-containing serine proteases appear to be involved either in a protease activation cascade or in extracellular matrix degradation. In addition, there are at least six members of the astacin subfamily of zinc metalloprotease which were found to contain this C1r/s domain. These include bone morphogenetic protein-1 (Wozney et al., Science 242: 1528-34 (1988)), and Drosophila tolloid gene, a dorsal-ventral patterning protein (Shimell et al., Cell 67: 469-81 (1991)), quail 1,25-dihydroxyvitamin D3-induced astacin like metallopeptidase that may play a role in the degradation of eggshell matrix, sea urchin blastula protease-10 (that could be involved in the differentiation of ectodermal lineages and subsequent patterning of the embryo), Xenopus embryonic protein UVS.2, a marker for developmental stage, and sea urchin VEB gene that is expressed in a spatially restricted pattern during the very early blastula stage of development. The majority of these C1r/s-containing, astacin metalloproteases appear to play a role in protein-protein interactions and embryonic development. The C1r/s domain has been also found in nonprotease proteins. These include neuropilin (A5 protein), a calcium-independent cell adhesion molecule that is developmentally-expressed in the nervous system and tumor necrosis factor-inducible protein TSG-6, a hyaluronate-binding protein that may be involved in cell-cell and cell-matrix interaction during inflammation and tumorigenesis.

FIG. 12 provides a schematic representation of the structures of matriptase. The protease consists of 683 amino acids, and the protein product has a calculated mass of 75,626. The protease contains two tandem complement subcomponent 1r and 1s domains (C1r/s) and four tandem LDL receptor domains. The scrine protease domain is at the carboxyl terminus.

An amino acid hydrophobic region was identified at the amino-terminus. This region is likely to serve as a signal peptide.

Example 3 Method of Using Matriptase as a Diagnostic Indicator

As indicated above, nipple aspirate, tissue biopsy, archival tissue, fluid from needle biopsy, or any biological sample containing cells or biological fluid can also be used as means of identifying the presence of matriptase in cells. The presence of matriptase can also be detected in tissue (e.g., epithelial cells) other than in the lactating breast. Given the plasma membrane localization, ECM-degrading activity and expression in breast cells of matriptase, forms of the protein and matriptase-protein complexes may be involved in cancer onset and progression, including cancer invasion and metastasis. Accordingly, agents which modulate matriptase activity or expression may be used to inhibit cancer onset and progression, or the onset and progression of other pathologic conditions.

One such compound is the soybean-derived, Bowman-Birk inhibitor (BBI) (Birk, Methods Enzymol. 45: 700-7 (1976)). BBI is an inhibitor of serine proteases and has previously been described to possess anti-cancer activity by preventing tumor initiation and progression in model systems (see, e.g., Kennedy et al., Cancer Res. 56: 679-82 (1996)). The finding that the matriptase in the tissue has different significance than the finding of matriptase in the completed form as found in human milk makes it possible to identify persons who would benefit from such inhibitors. For example, a method of treating malignancies and pre-malignant conditions of the breast comprises (1) identifying the presence of matriptase in breast tissue or fluid from the breast and, if such matriptase if found, administration of a tumor formation-inhibiting effective amount of BBI. A concentrate of BBI, BBIC, can be administered in dosage sufficient to obtain a blood level of 0.001 to 1 mM concentration of BBI in the blood as a means of inhibiting tumor initiation in a susceptible to breast cancer, as indicated by presence of matriptase in nipple aspirate or in tissue from biopsy, including tissue from needle biopsy. BBI can decrease matriptase activity in a dose-dependent manner, as indicated by fluorescent substrate assay and zymography in tumor initiation and progression model systems. BBI interacts directly with the serine protease active site on matriptase.

Example 4 Molecular Modeling of Forms of Matriptase

In this example, we set forth a method of identifying molecules (e.g., peptides and small compounds) that can interact with the complexed and uncomplexed forms of matriptase. By using molecular modeling, with the programs described herein or using other available programs, compounds can be identified that bind to the active site of matriptase or to other relevant sites on matriptase, such as C1r/C1s.

To understand molecular basis for the differential expression of a major uncomplexed matriptase in T-47D cells, we compared to a major complexed form in the lactating mammary gland. The interaction between matriptase and HAI-1 was investigated by comparing the structural differences between complexed and uncomplexed matriptase and by three-dimensional modeling of the interaction of the serine protease domain of matriptase with both Kunitz domains of HAI-1. These results revealed that complexed matriptase is in its activated, two-chain form, and that the Kunitz domain I of HAI-1 is likely to be the inhibitory domain for the enzyme.

Materials and Methods. Source of mAbs: Rat-derived, anti-matriptase mAb 21-9 was produced using matriptase isolated from T-47D breast cancer cells as immunogen, as described previously (see Lin et al., 1997 and related U.S. patent application Ser. No. 08/957,816 to Dickson et al. filed on Oct. 27, 1997). Mouse-derived anti-matriptase mAb M32 and anti-HAI-1 mAbs M58 and M19 were produced using 95-kDa matriptase/HAI-1 complex as immunogen, as described in Example 1.

Purification of matriptase from human milk, T-47D breast cancer cells, and MTSV 1.1 B milk-derived mammary epithelial cells—Matriptase is expressed by the lactating mammary gland, by SV40 T antigen-immortalized mammary luminal epithelial cells, and by human breast cancer cells. While the enzyme was detected in a complexed form in milk, it was a mixture of complexed and uncomplexed forms in MTSV 1.1B cells, and it was primarily in an uncomplexed form in T-47D cells. To purify the complexed matriptase, human milk was fractionated by CM-Sepharose chromatography, and the 95-kDa matriptase complex fractions were then loaded onto an anti-matriptase mAb 21-9-Sepharose immunoaffinity column, as described above in Example 1. Bound proteins were eluted by 0.1 M glycine buffer, pH 2.4, and stored in this low pH condition. To purify uncomplexed matriptase, the complexed matriptase and HAI-1 were first depleted by passing serum-free T-47 D cell-conditioned medium through an anti-HAI-1 mAb M58-Sepharose column. The unbound fraction (flow-through) was further loaded onto a 21-9-Sepharose column, and bound proteins were eluted by 0.1 M glycine buffer pH 2.4, as described previously (Lin et al., 1997). The eluted proteins were stored in low pH to prevent their degradation. A mixture of uncomplexed and complexed matriptase was purified from MTSV 1.1 B cell-conditioned medium by anti-matriptase 21-9-Sepharose immunoaffinity chromatography.

Diagonal gel electrophoresis: Two different types of diagonal gel electrophoresis were carried out, non-boiled/boiled and non-reduced/reduced. The non-boiled/boiled diagonal gel electrophoresis was used to examine the constituent components of matriptase/HAI-1 complexes and the non-covalent interaction between matriptase and HAI-1, as described in Example 1. Briefly, in the first dimension, the matriptase complexes were resolved in the absence of reducing agents by SDS polyacrylamide gel electrophoresis under non-boiled conditions. A gel strip was sliced out, boiled in SDS sample buffer in the absence of reducing agents, and electrophoresed on a second SDS polyacrylamide gel. To examine constituent components and their covalent interactions, matriptase samples from different sources were subjected to non-reduced/reduced diagonal gel electrophoresis. In the first dimension, matriptase was boiled in SDS sample buffer in the absence of reducing agents; in the second dimension, the gel strip was boiled in the presence of reducing agents.

Amino acid sequence analysis of the 45- and 25-kDa fragments of matriptase: Milk-derived 95-kDa matriptase complexes were purified using a combination of CM-Sepharose chromatography and anti-matriptase mAb 21-9-Sepharose immunoaffinity chromatography, as described above. Both 45- and 25-kDa fragments of matriptase were resolved by non-reduced/reduced diagonal gel electrophoresis, as described above, and then transferred to polyvinylidene fluoride (PVDF) membranes. The amino-terminal sequences of these two fragments were determined as described previously (Matsudaira, J. Biol. Chem. 262: 10035-38) (1987)) in the Howard Hughes Medical Institute Biopolymer Laboratory & W. M. Keck Foundation Biotechnology Resource Laboratory at Yale University.

Proteolytic activity of matriptase determined by cleavage of trypsin substrate. BOC-Gln-Ala-Arg-AMC: A variety of synthetic, fluorescent protease substrates with arginine or lysine as P1 sites can be cleaved by matriptase, as described in Example 2. Among these substrates, t-butyloxycarbonyl (BOC)-Gln-Ala-Arg-7-amino-4-methylcoumarin (Sigma; St. Louis, Mo.) is likely to be the best one. Using this substrate, matriptase was assayed in 20 mM Tris buffer pH 8.5 at 25° C. in a total volume of 200 μl. The final substrate concentration was 0.1 mM. The rate of cleavage was determined with a fluorescence spectrophotometer (Hitachi, F-4500).

Immunoblotting: Protein samples were resolved by 10% SDS-PAGE, transferred overnight to PVDF, and subsequently probed with mAbs, as indicated. Immunoreactive polypeptides were visualized using HRP-labeled secondary antibodies and the ECL detection system (Pierce, Rockford Ill.; NEN, Boston Mass.).

Preparation of M58-Sepharose column and immunoaffinity chromatography: An immunoaffinity matrix was prepared by coupling 5 mg of mAb M58/ml of CNBR-activated Sepharose 4B, as specified in the manufacturer's instructions (Pharmacia; Piscataway, N.J.). The immunoaffinity column was equilibrated with PBS, and the concentrated medium from T-47D human breast cancer cells was loaded onto a 1-ml column at a flow rate of 7 ml/h. The column was washed with 10 ml of 1% Triton X-100 in PBS and then 10 ml of PBS. Bound proteins were then eluted by 0.1 M glycine-HCl (pH 2.4), and fractions were immediately neutralized with 2 M Trizma base.

Northern analysis of HAI-2: Total RNA (10 μg) from T-47D cells was denatured and electrophoresed, and transferred to a nylon membrane. The membrane were hybridized with ³²P-labeled HAI-2 fragment, as described (Kawaguchi et al., J. Biol. Chem. 272: 27558-64 (1997).

Modeling: Homology modeling, as implemented in MODELLER (Sali et al., PROTEINS: Structure Function & Genetics 23: 318-26 (1995)) was chosen to build the three-dimensional structure of the serine protease domain (B chain) of matriptase and of the two Kunitz domains of HAI-1. The program BLAST (Altschul et al., Nucleic Acids Res. 25: 3389-3402 (1997)) was used to search the Protein Databank (PDB) (Bernstein et al., J. Mol. Biol. Chem. 112: 535-42 (1977)) for template proteins with known structures that have similar amino acid sequences to matriptase and to HAI-1. BLAST was also used to align all structures with the target sequence. Thrombin, entry 1hxe from PDB, with 34% identities, 53% positives and 6% gaps was found to be a good template for matriptase. The protease inhibitor domain of Alzheimer β-amyloid protein precursor, entry 1aap from PDB, with 45% identities and 56% positives was found to be a good template for the Kunitz domain of HAI-1. The same template, 1aap, with 45% identities and 62% positives, was used to build the structure of the Kunitz domain 2 of HAI-1. Hydrogens were assigned using HBUILD (Brunger et al., PROTEINS: Structure, Function & Genetics 4: 148-56 (1988) option within the CHARMM program. All structures were then refined using the program CHARMM (Brooks et al., J. Comput. Chem. 4: 187-217 (1983)) with the all atom parameter set CHARMM22 (MacKerell, Jr. et al., J Phys. Chem. 102: 3586-16 (1997). All structures were first minimized with 50 steepest descent steps and 500 adopted-basis Newton Raphson steps. Molecular dynamics, MD, simulations were used to further refine every structure. In MD simulations Ifs time step and a temperature of 300 K were used. The Hoenig salvation model (Sharp et al., Biochem. 30: 9686-97 (1991), as implemented in CHARMM, was used to represent the solvation effect. The protease-inhibitor complexes were built by orienting the inhibitor with the P1 residues, Arg-260 in Kunitz domain 1 and Lys-385 in Kunitz domain 2, in the direction of the S1 site of matriptase. The initial distance between the P1 residue and Asp-185, using B chain numbering, from the S1 site, was between 17-19 Å. Self-guided molecular dynamics simulation (SGMD) (Wu et al., J. Chem. Phys. 110: 9401-10 (1999)), which was shown to have a much better conformational search efficiency than the conventional MD method, was used to obtain the equilibrated structure of the complex between the serine protease domain of matriptase and the Kunitz domains of HAI-1. A restraining potential was applied to gradually decrease the distance between the guanidino or amino group of the P1 residue from HAI-1 and the carboxyl group of Asp-185 from matriptase. The final distance between the two residues was set to be between 2.2 and 6.0 Å, as observed in the X-ray structure of the trypsin complex with the soybean trypsin inhibitor, entry 1avw in PDB (Bernstein et al., 1977). Matriptase was fixed for the first 100 to 280 ps to save computer time. This was followed by 100 ps SGMD, without constraining matriptase.

Results. Complexed matriptase is an activated, two chain form, but the majority of the uncomplexed enzyme is in a single chain, zymogen form: In Examples 1 and 2, matriptase was detected in T-47D cells mainly as an uncomplexed form, compared to a 95-kDa complex with a 40-kDa fragment of HAI-1 in human milk. The strong interaction between matriptase and HAI-1 could be dissociated after boiling in the absence of reducing agents. Because HAI-1 was also detected mainly in its uncomplexed form in T-47D cells, the interaction between matriptase and HAI-1 appeared not to occur. Some serine protease inhibitors, such as bovine pancreatic trypsin inhibitor (Ruhlmann et al., J. Mol. Biol. 77: 417-36 (1973)) and squash seed protease inhibitor (Zbyryt et al., Biol. Chem. Hoppe Seyler 372: 255-62 (1991)), are able to bind to the latent form of serine proteases, such as trypsinogen. However, for most of the serine proteases, cleavage of the enzyme at a canonical activation motif, resulting in proper formation of a substrate binding pocket, is required for their binding to serine protease inhibitors. Therefore, lack of interaction between T-47D cell-derived matriptase and HAI-1 could result from fact that the majority of matriptase produced by T47D cells is in the single chain, zymogen form. In contrast, complexed matriptase, isolated from human milk, is likely to be in its activated, two-chain form. In addition, matriptase was detected in a mixture of complexed and uncomplexed forms in MTSV 1.1 B, milk-derived, SV-40 immortalized mammary epithelial cells (see Example 1). This could result from a mixture of latent and activated matriptase produced by these cells. To further test this hypothesis, we have isolated matriptase from three sources, and these three matriptase preparations were subjected to non-reduced/reduced diagonal gel electrophoresis. In this electrophoresis assay, proteins that contain multiple disulfide-bonded components are dissociated into the constituent components, that appear on the same electrophoretic path. In contrast, single-chain proteins are not dissociated. The complex-derived matriptase (from milk) was converted to two groups of polypeptides with apparent sizes of 45-kDa (A chain) and 25-kDa (B chain). In contrast, the uncomplexed matriptase (from T-47D cells) was observed as a single chain, with apparent size of 70-kDa in this diagonal gel electrophoresis system. Consistently, a mixture of single-chain matriptase and two-chain matriptase was observed for preparations isolated from MTSV 1.1 B cells. These results suggest that complexed matriptase is a two-chain protease, whereas uncomplexed matriptase is a single-chain protein.

To determine the position of the cleavage site for the generation of the two-chain form of matriptase, the 45- and 25-kDa components were each subjected to N-terminal amino acid sequence analyses. The amino acid residues obtained from the 25-kDa B chain were VVGGTDADEGEWP. This sequence begins with the likely cleavage site within the activation motif in matriptase. When the 45-kDa A chain (including two major plus one minor spots) was sequenced, two overlapping sequences (SFVVTSVVAFPTDSKTVQRT; TVQRTQDNSCSFGLHARGVE) were obtained, and both matched sequences close to the amino terminus of matriptase. These two different amino-terminal sequences may be derived from the two major spots of matriptase A chain and suggest that the different migration rates of the two components result from their different amino termini.

Inhibition of matriptase activity by the interaction with HAI-1: HAI-1, a protein containing contains two protease inhibitory domains (Kunitz domains), was initially identified as a binding protein of matriptase. However, gelatinolytic activity was observed for the 95-kDa matriptase/HAI-1 complex, as described in Example 2. Because Kunitz inhibitors are known to bind and inhibit scrine proteases in a reversible and competitive mode, the gelatinolytic activity of the 95-kDa matriptase/HAI-1 complex could result from the excessive levels of substrate (1 mg/ml of gelatin) under the conditions of zymography. Therefore, to demonstrate that HAI-1 is an inhibitor of matriptase activity, we took advantage of the fact that the interactions between serine proteases and Kunitz-type inhibitors are acid sensitive and reversible. Both matriptase and HAI-1 were co-purified from human milk by immunoaffinity chromatography and maintained in their uncomplexed status in glycine buffer pH 2.4. When this matriptase/HAI-1 preparation was brought to pH 8.0 and incubated at 37° C., the interaction between matriptase and HAI-1 (in the 95-kDa complex) was observed to occur after incubation time as short as 5 min. The uncomplexed matriptase became undetectable by immunoblot after 30 and 60 min. of incubation (FIG. 13A). Strong gelatinolytic activity was observed for the uncomplexed matriptase in a gelatin zymogram (FIG. 13B), in contrast to the trace amounts of gelatinolytic activity that were observed for the 95-kDa complex. In addition, the rate of cleavage of a synthetic, fluorescent substrate by matriptase was decreased following complex formation (FIG. 13C). These results provide direct evidence that HAI-1 is an inhibitor of matriptase and that the interaction of these two molecules results in catalytic inhibition that is acid sensitive and reversible.

Different matriptase/HAI-1 complexes result from the binding of matriptase with different fragments of HAI-1: In Example 1, two matriptase/HAI-1 complexes were purified from human milk: (1) a 95-kDa complex containing matriptase and a 40-kDa fragment of HAI-1 and a 85-kDa complex containing matriptase and (2) a 25-kDa fragment of HAI-1. In contrast, in T-47D breast cancer cells, two matriptase complexes with apparent sizes of 95- and 110-kDa were detected by anti-matriptase mAb (Lin et al., 1997). These two complexes were also recognized by anti-HAI-1 mAbs, suggesting that the T-47D cell-derived 110- and 95-kDa matriptase complexes contain HAI-1. The 95-kDa complex could contain matriptase and the 40-kDa HAI-1 fragment, as does the milk-derived 95-kDa complex. However, the components of the 110-kDa complex are not clear. Thus, to investigate the components of these two complexes, a combination of immunoaffinity purification using anti-HAI-1 mAb M58-Sepharose and non-boiled/boiled diagonal gel electrophoresis was performed. As expected, both 110- and 95-kDa complexes were purified by anti-HAI-1 mAb M58-Sepharose. In addition to these complexes, two major HAI-1 fragments, with apparent sizes of 50-kDa and 40-kDa, as well as minor ones between them, were purified by immunoaffinity chromatography and verified by immunoblot. Both purified 110- and 95-kDa complexes were capable of dissociation by boiling in the absence of reducing agents, and matriptase was likely to be released from these two complexes.

To further investigate whether the 50- and 40-kDa HAI-1 fragments are the constituent subunit(s) of the 110- and 95-kDa complexes, respectively, both complexes were subjected to non-boiled/boiled diagonal gel electrophoresis (FIG. 4). The 95-kDa complex was converted, by boiling, to matriptase and to a 40-kDa protein that exhibited the same migration rate as the 40-kDa fragment of HAI-1. The 110-kDa complex was converted, by boiling, to matriptase and to a 50-kDa protein, whose migration rate is the same as that of the 50-kDa fragment of HAI-1. Because both 110- and 95-kDa complexes were captured by immobilized anti-HAI-1 mAb M58 (immunoaffinity chromatography) and detected by immunoblot analysis using another anti-HAI-1 mAb M19, these 50- and 40-kDa proteins are likely to be HAI-1 fragments that interact with the anti-HAI-1 mAbs. This observation suggests that the cancer cell-derived 95-kDa matriptase complex resembles the one previously isolated from milk as described in Example 1, and contains matriptase bound to the 40-kDa fragment of HAI-1. The 110-kDa complex contains the 50-kDa fragment of HAI-1.

Three-dimensional structure of B-chain of matriptase and HAI-1 as deduced by molecular modeling: To gain a better understanding of the interaction between matriptase and the two Kunitz domains of HAI-1, we utilized homology modeling to depict the three-dimensional structures of the serine protease domain of matriptase (B-chain) and of both Kunitz domains of HAI-1. Human thrombin was used as a template protein for matriptase. Since the sequence identity and similarity between matriptase and human thrombin are 34% and 53%, respectively, the 3D structure of matriptase can be accurately modeled. The protease inhibitor domain of Alzheimer's amyloid β-protein was used as template protein for Kunitz domains 1 and 2 of HAI-1, respectively. The sequence identities of Kunitz domains 1 and 2 with the protease inhibitor domain of Alzheimer's amyloid β-protein are 45% and the modeled structures are expected to have a main-chain RMS error as low as IA for 90% of the residues (SalI, Curr. Opin. Biotech. 6: 437-51 (1995)).

Based on the high sequence identity between matriptase and trypsin, thrombin, and factor Xa, we propose that conserved Cys residues should form conserved disulfide bonds. Thus, the serine protease domain (B-chain) of matriptase is likely to have three disulfide bonds: Cys-27 and Cys-43, Cys-162 and Cys-166, Cys-187, and Cys-216 (the numbers of residues were designated based on the B-chain itself). Residues Ser-191, His-42, and Asp-97 form the catalytic triad center and are positioned on the surface of the enzyme. The disulfide bond between Cys-27 and Cys-43 stabilizes the position of His-42, as in trypsin. A negatively charged residue, Asp-185, is located at the bottom of the S1 binding site, which is consistent with the experimental data showing the preference of matriptase for substrates with positively charged residues, Arg/Lys at the P1 position (Example 2). The disulfide bond between Cys-216 and Cys-187 and the hydrogen bond between Asn-220 and Ser-188 stabilize the position of Asp-185, as in trypsin. Gly-215, Cys-216, Ala-217 and Gln-218 are at the entrance of the S1 binding pocket. The S1′ pocket is proposed to be marked by Leu-18, Ala-20, Leu-21, Ile-26 and Trp-58, which form a hydrophobic binding site. The disulfide bond between Cys-27 and Cys-43 stabilizes the position of Ile-26. This may be important for the geometry of the binding site. In addition to these features, it is proposed that matriptase has a negatively-charged binding site, formed by Asp-46, Asp-47 and Asp-91.

Using the same approach as for matriptase, the position of disulfide bonds in the Kunitz domains 1 and 3 of HAI-1 were assigned. The three disulfide bonds in Kunitz domain 1 are between Cys-275 and Cys-296, Cys-250 and Cys-300, Cys-283 and Cys-259. The disulfide bond between Cys-250 and Cys-300 bridges the terminal sections of this domain, and the disulfide bond between Cys-259 and Cys-283 stabilizes the position of Arg-260 (P1 residue), Arg-258 and Leu-284 (P1′ residue).

The structure of the Kunitz domain 2 of HAI-1 also has three disulfide bonds, Cys375-Cys425, Cys384-Cys408, Cys400-Cys421. The disulfide bond between Cys-375 and Cys-425 bridges the terminal sections of Kunitz domain 2. The disulfide bond between Cys-384 and Cys-408 stabilizes the position of Lys-385 (P1 residue) and Leu-383 (putative P1′ residue). It should be noted that the position of Leu-383 corresponds to that of Arg-258 from Kunitz domain 1. The residue corresponding to Leu-284 from Kunitz domain 1 is Tyr-409. These two structural alterations may influence the binding of the Kunitz domain 2 to matriptase.

Interactions between matriptase and both Kunitz domains of HAI-1 as determined by molecular modeling: The equilibrated structure of the complex between the Kunitz domain 1 and matriptase reveals that salt bridges are the major binding forces between the two proteins. It is important to note that Arg-258 and Arg-260 bind to Asp residues that are about 20 Å apart. Arg-260 of HAI-1 binds to the S1 site of matriptase, while Arg-258 of HAI-1 binds to the negatively-charged binding site of matriptase. A similar binding mode was previously observed in the X-ray structure of trypsin complexed with soybean trypsin inhibitor (Bernstein et al., 1977). In both cases, the two Arg residues, separated by Ile in soybean trypsin inhibitor and by Cys in HAI-1, bind to Asp residues that are distant in the protease. In addition to salt bridges, a hydrophobic interaction was observed between Leu-284 of HAI-1 and the hydrophobic pocket, formed by Ala-20, Ile-26 and Trp-58 in matriptase. This suggests that matriptase may prefer substrates with a hydrophobic P1′ residue and that the size of that residue is determined by the size of the S1′ site.

In the complex between matriptase and the Kunitz domain 2 of HAI-1, the P1 residue, Lys-385, binds more weakly to the S1 site than does Arg-260 from Kunitz domain 1, because bidentate interactions between oppositely charged groups are known to be more stable than monodentate interactions. This was previously observed for a series of thrombin inhibitors. For example, DuP714, with Arg as P1 residue, has a K_(i) value that is 6 times lower than the analog with Lys as P1 residue (Weber et al., Biochem. 34: 3750-7 (1995). In addition to weaker interaction between the P1 site (Lys-385) of the Kunitz domain 2 and the S1 site (Asp-185) of matriptase B-chain, the negatively charged residue (Glu-386) next to the P1 residue in Kunitz domain 2 may also decrease the binding of Lys-385 to the S1 site. In contrast, the corresponding residue in Kunitz domain 1 is Gly-261, which is non-charged and the smallest residue. Another possibly important residue is Leu-383; this residue binds weakly to the putative S1′ site, suggesting the importance of this site for substrate recognition (in addition to the S1 site). This residue corresponds to Arg-258 from the Kunitz domain 1 of HAI-1, suggesting that the Kunitz domain 2 of HAI-1 binds in a distorted orientation to matriptase; this may further decrease its affinity for matriptase, when compared to Kunitz domain 1. Tyr-409 binds to the top of the putative S1′ binding site. Tyr-409 is connected to Leu-383 through the Cys-384-Cys-408 disulfide bond, thus not allowing Leu-383 to interact properly with the putative S1′ site, since the positions of the two residues are interconnected. In summary, our results showed that HAI-1 Kunitz domain 1 has a much better interaction with matriptase than HAI-1 Kunitz domain 2.

In Example 2, matriptase was observed to exhibit trypsin-like activity, both in terms of its primary cleavage at arginine residues and in its rather loose selectivity for substrate P2 sites. The gelatinolytic activity of matriptase is likely to be attributed to this broad spectrum cleavage activity. Thus, it appears likely that precise mechanisms, whereby the potent proteolytic activity of matriptase can be regulated, would be required in order to prevent unwanted proteolysis. Matriptase, like most of other serine proteases, may be synthesized as a single-chain zymogen, lacking binding affinity to its cognate inhibitor, HAI-1. A likely mechanism for activation of matriptase is the conversion of single-chain matriptase into a two-chain form, by cleavage at the activation motif. Thus, proteolytic activation of matriptase is likely to be an irreversible process; interaction of the enzyme with its Kunitz-type inhibitor could provide an important inhibitory control to prevent unwanted proteolysis. In support of this hypothesis is the fact that the majority of matriptase was detected either in an uncomplexed single-chain form or in a two-chain form that was observed to be tightly bound with its inhibitor.

During lactation, remodeling of mammary basement membrane is enhanced (Beck et al., Biochem. Biophys. Res. Commun. 190: 616-23 (1993)), and proteases have been implicated in this process (Talhouk et al., Development 112: 439-49 (1991)). Identification of matriptase in human milk suggests that this enzyme could play a role in tissue remodeling and in other aspects of lactation. This hypothesis has been further confirmed by the fact that matriptase was identified specifically as an activated, two-chain form in human milk, and suggests that activation of the protease is enhanced during lactation. While matriptase is activated, in the lactating mammary gland, it is inhibited by binding to HAI-1. These results further suggest that matriptase is likely to be synthesized as a zymogen, activated only at the proper time and in the proper place, then inhibited by HAI-1 in order to prevent unwanted proteolysis, and finally released as a matriptase/HAI-1 complex in milk.

In T-47D breast cancer cells, single-chain matriptase is the major form of the protease, and its complexes (110- and 95-kDa) can also be easily detected by immunoblot. Nevertheless, matriptase was initially identified in this cell type as the major gelatinolytic activity, as assessed by gelatin zymography (Shi et al., Canc. Res. 53: 1409-15 (1993)). These results suggest that the single-chain matriptase may be enzymatically active or that there is a trace amount of two-chain, active matriptase with a similar size to single-chain matriptase expressed by T-47D cells. The former possibility may be unlikely, because high levels of single-chain matriptase and HAI-1 coexist in their uncomplexed forms, where the active site triad and substrate binding pocket of single-chain matriptase may not be well-formed. The existence of a low level of two-chain matriptase, which contributes to the gelatinolytic activity found in T-47D cells, may be more likely. It is necessary to have single-chain matriptase without contamination of two-chain matriptase in order to carry out experiments to fully prove single-chain matriptase to be latent. Expression of matriptase with a point mutation at the activation site could be the most convincing way to obtain single-chain matriptase without contamination of two-chain matriptase.

HAI-1 is likely to be synthesized as a 55-kDa, integral membrane protein, based on a putative transmembrane domain at its C-terminus (Shimomura et al., J. Biol. Chem. 272: 6370-6 (1997). This is supported by the observations that the apparent size of the membrane-bound inhibitor is 55-kDa and that the association of the inhibitor with the membrane fraction resists a wash of 2 M KCl; these are characteristics of an integral membrane protein. The 50-kDa fragment of HAI-1 is likely to be a cleaved form of HAI. The cleavage site is likely to be near to the transmembrane domain, since the 50-kDa fragment was detected as a major form of the inhibitor in conditioned media of T-47D cells. The 50-kDa HAI-1 is likely to have both Kunitz domains and the LDL receptor domain, and to be able to interact with matriptase to form the 110-kDa complex.

Further degradation of the 50-kDa HAI-1 fragment also could occur at the C-terminus, probably within the Kunitz domain 2, to generate the 40-kDa fragment. Since the amino-terminal sequence of the 40-kDa fragment was identified to be GPPPAPPGLPAG (Example 2; and Shimomura et al., (1997)), this fragment is not big enough to cover the entire Kunitz domain 2 (Shimomura et al., (1997)). Thus, the 40-kDa HAI-1 fragment is likely to contain only one intact Kunitz domain (domain 1) and the LDL receptor domain. This 40-kDa HAI-1 fragment is also able to complex with matriptase to form the 95-kDa species. The 25-kDa fragment, which still exhibits binding affinity to matriptase discussed in Example 1, is likely to be generated by cleavage of the 40-kDa inhibitor fragment at the Arg-153 of HAI-1, because the first seven amino-terminal residues were identified to be a sequence spanning residues 154 through 160 of the inhibitor. In common with the 40-kDa inhibitor fragment, the 25-kDa fragment contains only the Kunitz domain 1 and an LDL receptor domain; it is able to interact with matriptase to form an 85-kDa complex. These observations suggest that the Kunitz domain 1, but not domain 2 is likely to be the inhibitory domain for matriptase. The proposed processing of matriptase and its inhibitor, and their interactions, are summarized in FIG. 14.

The hypothesis that the Kunitz domain 1 of HAI-1 is the one which may be responsible for inhibition of matriptase is further supported by observations from computer modeling. Since both the Kunitz domains 1 and 2 contain positively charged P1 residues (Arg-260 domain 1 and Lys-385 in domain 2), they each have the potential to inhibit trypsin-like serine proteases, such as matriptase, by using these residues to engage the substrate-binding pocket. In the Kunitz domain 1, the second salt bridge not only stabilizes the complex but also orients the inhibitor, so that it blocks access of substrates to the active site. This interaction is missing in the complex with Kunitz domain 2. Therefore, Kunitz domain 1 appears to be the one that is responsible for the formation of a stable complex with matriptase. This suggestion is consistent with the observation that the 40- and 25-kDa fragments of the inhibitor were able to form stable complexes with matriptase.

The second salt bridge was identified to be Arg-258 of the inhibitor, binding to the anionic site of matriptase. A search for proteins which contain potential anti-trypsin-like serine protease Kunitz domains (Arg or Lys at P1 site) was carried out in GenBank. We identified a second Kunitz-type inhibitor containing an Arg residue in the corresponding position of Arg-258 of HAI-1 in Homo sapiens. This protein, identified by different groups, has three accession numbers (ABOO6534; U78095; and AF027205) in GenBank, and was named placental bikunin (Marlor et al., J. Biol. Chem. 272: 12202-8 (1997)) or HGF activator inhibitor 2 (EAI-2) (Kawaguchi et al., J. Biol. Chem. 272: 27558-64 (1997)). HAI-2, like HAI-1 was identified from MKN 45 human stomach carcinoma cells and shown to be an inhibitor of HGF activator (Kawaguchi et al., (1997). HAI-2 resembles HAI-1 in terms of its transmembrane domain and its two Kunitz domains. HAI-2 was also isolated from human placenta. Because it contained two Kunitz domains, it was also named placenta bikunin (two Kunitz domains). In addition to its blockade of HGF activator, placenta bikunin exhibits strong inhibition of human plasmin, human tissue kallikrein, human plasma kallikrein, and human factor XIa (Delaria et al., J. Biol. Chem. 272: 12209-14 (1997)).

The third important binding force identified between matriptase and the Kunitz domain 1 is a hydrophobic interaction between Leu-284 of the inhibitor and a hydrophobic pocket in matriptase, delimited by Leu-18, Ala-20, Ile-26 and Trp-58. The corresponding residue for this Leu-284 in the Kunitz domain 1 of placental bikunin/HAI-2 is Asp-72, a negatively charged residue, suggesting that this hydrophobic interaction may not occur when matriptase encounters placental bikunin/HAI-2. Thus, matriptase may have a weaker interaction with placenta bikunin/HAI-2 compared to its cognate inhibitor (HAI-1). This notion is supported by the observation that, although both matriptase inhibitor (HAI-1) and placenta bikunin/HAI-2 were expressed by T-47D cells and by MTSV 1.1 B cells, as determined by Northern analysis. Only HAI-1 has been identified to be in complexes with matriptase.

Although the stoichiometries of the components of the 110- and 95-kDa matriptase/HAI-1 complexes have not been directly determined, matriptase (70-kDa apparent size) and HAT-1 (40- and 50-kDa fragments) are likely to bind to each other in a 1:1 ratio, based on their sizes and the sizes of resultant complexes. We note that only a small amount of the 40-kDa HAI-1 fragment, relative to matriptase, was dissociated from the 95-kDa matriptase complex by boiling. This appearance of a relatively small amount of 40-kDa protein could result from its small size and its likely weaker affinity to Coomassie Blue. The binding between matriptase and HAI-1 appears to cause a more compacted configuration of these two proteins, and thus on gel electrophoresis the apparent sizes of the matriptase/HAI-1 complexes are smaller than those of the sum of their components.

Both matriptase and its cognate inhibitor are likely to be biosynthesized as integral membrane proteins. The “TM” indicates the location of the transmembrane domain. “I” stands for Kunitz domain 1; “II” for Kunitz domain 2; and “L” for LDL receptor domain. The proposed processing steps for both proteins are described in Example 4.

Example 5 Production of mAbs which are Specifically Directed Against Active, Two-Chain Matriptase

In order to investigate activation of matriptase, we obtained two anti-matriptase mAbs which specifically recognize the two-chain matriptase, but not the single-chain form (FIG. 17). Activation of matriptase, like other serine proteases may require cleavage of a single specific peptide bond in the canonical activation motif. This cleavage not only transforms catalytically inactive serine proteases into active forms but also triggers discrete, highly localized conformational changes. Thus, mAbs directed against these activation-associated conformational changes are theoretically able to distinguish the active matriptase from its latent form. In our previous studies, more than 80 hybridoma clones were generated using 95-kDa matriptase/KSPI complex as immunogens. Hybridomas were selected for the mAbs capable of recognizing the 95-kDa matriptase/KSPI complex under non-boiled conditions and uncomplexed matriptase after boiling. These anti-matriptase mAbs were further tested using the conditioned medium of T-47D breast cancer cells to select mAbs which are able to distinguish complexed matriptase (e.g., a two-chain form) from uncomplexed matriptase (e.g., a single-chain form). In the cell-conditioned medium of T-47D cells, matriptase was expressed predominantly in uncomplexed, single-chain form and in two minor matriptase/KSPI complexes with apparent sizes of 110- and 95-kDa. Uncomplexed, active matriptase is also likely to exist and was detected as a major gelatinolytic activity by gelatin zymography. For most of these anti-matriptase mAbs as represented here by mAb M130 (FIG. 17, lane 1), matriptase was detected mainly in an uncomplexed form and two complexed forms (110- and 95-kDa), which can be dissociated after boiling (FIG. 17, lane 2). In contrast, although mAb M123 (IgG₁) recognized the 95- and the 110-kDa matriptase complexes (FIG. 17, lane 3) as well as mAb M130, mAb M123 recognized the uncomplexed matriptase more weakly than mAb M130 as demonstrated by the weaker band (FIG. 17, lane 3). The immunoreactive signals of 110- and 95-kDa matriptase complexes were converted to matriptase after boiling (FIG. 17, lane 4). To further characterize mAbs M123 and M69 (IgG₁), another mAb was selected (M32), which is specifically directed against two-chain matriptase. We compared the immunoreactivity of the antibodies using purified, two-chain matriptase from human milk and single-chain matriptase, purified from T-47D cells. Both milk-derived and T-47D-derived matriptase were recognized by anti-matriptase mAb M32 (FIG. 17, lanes 5 and 6, respectively); however, mAbs M123 (FIG. 17, lanes 7 and 8, respectively) and mAb M69 (FIG. 17, lanes 9 and 10) only recognized the two-chained form of matriptase. Moreover, the two-chain form of matriptase appears to have a slower migration rate than that of the single-chain form of matriptase (FIG. 17, compared lane 5 with lane 6).

Although the present invention has been described in detail with reference to examples above, it is understood that various modifications can be made without departing from the spirit of the invention. All cited patents and publications referred to in this application are herein incorporated by reference in their entirety. Also incorporated herein by reference in their entirety are the following related U.S. applications and patent: U.S. Ser. No. 60/124,006 filed Mar. 12, 1999; U.S. Pat. No. 5,482,848 to Dickson et al. which issued on Jan. 9, 1996; and U.S. Ser. No. 08/957,816 to Dickson et al., filed on Oct. 27, 1997. 

1.-8. (canceled)
 9. A nucleic acid comprising SEQ ID NO: 4 or SEQ ID NO:
 26. 10. A vector comprising the nucleic acid of claim
 9. 11. A cell transformed with the nucleic acid of claim
 9. 12.-33. (canceled)
 34. A nucleic acid which encodes the amino acid sequence set forth in SEQ ID NO: 5 or SEQ ID NO:
 27. 35. A vector comprising the nucleic acid of claim
 34. 36. A cell transformed with the nucleic acid of claim
 34. 37. A nucleic acid which is complimentary to the nucleic acid of claim 9 or claim
 34. 38. A nucleic acid which hybridizes under stringent conditions to the nucleic acid of claim 9 or claim
 34. 